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course Phy 202
4/4 9This assignment is not complete, but I want to submit what I do have for feedback so I will know where to go. i looked at the posted class notes, but I have a hard time differentiating between us and Univeristy
3.21.11
The following can all be answered using general knowledge of basic quantities like Newtons, Joules, watts, and general knowledge of first-semester physics. The main focus here is on reasoning. Formulas are unnecessary and should not be used. You shouldn't have to, but if you forget what a watt is, or a Joule, you can look up those definitions.
A 1-amp current in a straight 1-meter wire in a uniform 1-Tesla magnetic field perpendicular to the wire experiences a force of 1 Newton, in a direction perpendicular to both the wire and the magnetic field. The direction of the force is found by the right-hand rule, taking the cross product of the current flow vector with the magnetic field vector.
To begin to make sense of all this statement work through the following:
`q001. How much force would you expect to result from each of the following, assuming the wire to be straight, and the current and magnetic field vectors to be perpendicular?
A 1-amp current in a 1-meter wire in a .01-Tesla magnetic field.
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.01 N
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A 250-milliamp current in a 1-meter wire in a 1-Tesla magnetic field.
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.25 N
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A 1-amp current in a 1-centimeter wire in a 1-Tesla magnetic field.
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.01 N
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A 250-milliamg current in a 1-centimeter wire in a .01-Tesla magnetic field.
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2.5 x 10^-5 N
@& Good.*@
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`q002. What would be the direction of the force on the current in each of the following scenarios?
The current is directed toward the north and the magnetic field is upward.
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The current is directed toward the west and the magnetic field is downward.
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The current is directed toward the east and the magnetic field is directed toward the west.
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The current is directed upward and the magnetic field is directed toward the south.
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@& For example:
The force on a current to the west and a downward magnetic field is found by crossing the current with the field. The right-hand rule tells us that the direction of the force is in this case to the south.*@
`q003. A square loop of wire is balanced on a thin wood beam, with the beam in the north-south direction and two of the sides of the loop parallel to the beam. A uniform magnetic field is directed downward. A switch is thrown, causing a current to run through the loop in the clockwise direction. The force exerted on the loop is much less than its weight, so the loop will not lift off of the beam.
The four sides of the loop will be referred to as the north, south, east and west sides.
What will be the direction of the force exerted on the north side of the loop?
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inward
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What will be the direction of the force exerted on the south side of the loop?
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inward
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What will be the direction of the force exerted on the east side of the loop?
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inward
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What will be the direction of the force exerted on the west side of the loop?
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inward
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What effect would these forces have on the loop?
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The loop will want to collapse
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Answer the same questions, assuming that the magnetic field is now directed toward the west.
What will be the direction of the force exerted on the north side of the loop?
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What will be the direction of the force exerted on the south side of the loop?
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What will be the direction of the force exerted on the east side of the loop?
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What will be the direction of the force exerted on the west side of the loop?
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What effect would these forces have on the loop?
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@&
For example, with the magnetic field directed toward the west:
In the north side of the loop the clockwise flow results in a current toward the east. Crossed with the westward field the force will be zero.
In the east side of the loop the clockwise flow results in a current toward the south. Crossed with the westward field the force will be upward, tending to rotate the loop counterclockwise relative to its south-to-north axis.
*@
`q004. A simple pendulum of mass .1 gram and length 10 cm is pulled back 1 cm from its equilibrium position.
How much force is required?
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9.8 x 10 ^-5 N
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If this force is the result of a .15 amp current flowing through a 2-cm length of straight wire, in a magnetic field perpendicular to the wire, what is the magnetic field?
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@&
Consistent with your answers to the first question regarding forces on current segments:
The force on current I through wire of length `dL in magnetic field B, with wire perpendicular to field, is
F = I `dL B.
Review the first question to make sure you understand this in the context of that question.
Then see if you can use the relationship to answer the question.*@
`q005. The Coulomb is a unit of electric charge. Two charges, each of 1 microCoulomb and each confined to a very small sphere which can be considered to be a point, with the spheres separated by 10 cm, will exert a force of magnitude .9 Newtons. The force decreases as the distance between the spheres increases, and increases as that distance decreases. The force is inversely proportional to the distance between the spheres. The interaction is completely analogous to the gravitational interaction between two masses, except that the force can be one of attraction or repulsion, depending on the signs of the two charges (i.e., whether each is positive or negative).
How much force would you expect if one of the forces was increased to 10 microCoulombs, with the other remaining the same?
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How much force would you expect if the other force was then increased to 10 microCoulombs?
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Returning to the original 1 microCoulomb charges and 10 cm distance:
How much force would you expect if the distance was doubled to 20 cm?
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How much force would you expect if the distance was halved to 5 cm?
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How much force would you expect if the distance was increased by a factor of 10, to 100 cm?
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How much force would you expect if the distance was decreased by a factor of 10, to 1 cm?
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What force would you expect if the charges were both 1 Coulomb and the separation was 1 meter?
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@& See if these partial solutions help:
Increasing one of the charges by a factor of 10 increases the force by a factor of 10, from .9 N to 9 N.
If the other charge is then increased by a factor of 10 the what will happen?
Doubling the distance between the two original charges increases the squared distance by a factor of 4, which decreases the force by a factor of 4, from .9 N to .225 N.
Decreasing the distance between the two original charges by a factor of 10 decreases the squared distance by a factor of 100, which increases the force by a factor of 100, from .9 N to 90 N.
*@
`q006. An amp (short for 'Ampere') is a flow of 1 Coulomb of charge per second. 1 Coulomb of charge is about 6 * 10^18 fundamental charges, where the fundamental charge is the magnitude of the charge on an electron.
How many Coulombs of charge flow in 1 minute through a circuit in which the current is .25 amps?
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How long would it take for an Avogadro's number of electrons to flow through this circuit?
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`q007. A Coulomb of charge flowing through 1 volt has a potential energy change of 1 Joule. What potential energy change would you expect for each of the following situations?
.25 Coulombs of charge flow through 1 volt.
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.20 Coulombs flow through a 1.5 volt battery.
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A current of .25 amps flows through a 1.5 volt battery for 60 seconds.
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`q008. How many amps must flow through a 110-volt circuit to produce 200 watts of power?
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@& I've inserted notes on some of the questions. They should help get you moving on some of the places where you might be stuck.*@
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Self-critique (if necessary):
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Self-critique rating:
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@& Here are detailed explanations of the 21 circuits (explanation of each under corresponding 'given solution')
`q001. Does the current pass through the bulb?
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Your solution:
Confidence rating:
Given Solution: The current flows from the generator to the positive generator lead, through the red wire, through the bulb, through the black wire and to the negative generator lead, then back through the generator. There is no break in the circuit, and there is no point at which the current can branch off and avoid the bulb. The current therefore passes through the bulb.
Self-critique (if necessary):
Self-critique rating:
Question:
`q002. Trace the current in this circuit.
Does current pass through both bulbs?
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If one bulb was disconnected, would current still flow?
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Is there a direct connection between the first bulb and the generator? A direct connection is one in which you can get from one side of the bulb to one terminal of the generator without passing through anything but conducting wire (e.g., without passing through another bulb or other circuit element), and from the opposite side of the bulb to the opposite terminal of the generator, again without passing through anything but wire.
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Is there a direct connection between the second bulb and the generator?
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Your solution:
Confidence rating:
Given Solution:
The circuit is unbroken and unbranched. The current flows from the positive generator lead through the red and white wires, the first bulb, the green wire, the second bulb, and the black wire to the negative generator lead, from which it passes back through the generator.
The first bulb has a direct unhindered path through the white and red wires to the positive lead of the generator. However its path to the negative lead passes through the second bulb, so the first bulb is not directly connected to the generator.
Neither is the second bulb. It does have a direct connection to the negative lead of the generator, but its connection to the positive lead passes through the first bulb.
Self-critique (if necessary):
Self-critique rating:
Question:
`q003. Now trace the current in this circuit.
Does current pass through both bulbs?
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Is it possible to disconnect one bulb, but have the current still flow through the other?
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Is there a direct connection between the first bulb and the generator?
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Is there a direct connection between the second bulb and the generator?
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Your solution:
Confidence rating:
Given Solution:
Current flows from the positive terminal of the generator through the red wire, where it branches, with current able to pass through the first bulb or through the white wire to the second bulb. Current which passes through the first bulb can then pass through the black wire to the negative generator lead. Current which branches through the white wire to the second bulb passes through that bulb, into the green wire, then through the black wire to the negative generator lead.
The first bulb has a direct connection to the generator through the red wire on the positive generator lead, and through the black wire on the negative generator lead.
The second bulb has a direct connection to the positive generator lead, through the white and the red wires, and to the negative generator lead, through the green and black wires.
Self-critique (if necessary):
Self-critique rating:
Question:
`q004. Now there's a meter in the circuit. The red lead of the meter is connected to the 'red' side of the bulb, the black lead to the 'black' side.
Does the meter have a direct connection to the generator?
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How many possible paths can the current take through the circuit?
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If the leads of the meter are removed, will current still flow through the circuit?
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Your solution:
Confidence rating:
Given Solution:
The red lead of the generator is in contact with the red wire, and through it to the positive lead of the generator. The black generator lead is in contact with the black wire attached to the negative lead of the generator. So the meter is directly connected to the generator.
The current branches at the first bulb, with possible paths through the first bulb, the second bulb, and the generator. There are three possible paths.
If the leads of the generator are removed, both bulbs are still connected as they were previously, and current flows through the bulbs.
Self-critique (if necessary):
Self-critique rating:
Question:
`q005. Does the meter now have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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The red lead of the meter is directly connected to the positive lead of the generator, the black lead of the meter to the negative generator lead. The meter therefore has a direct connection to the generator.
If the leads are removed both bulbs are still directly connected to the generator and current will flow through both.
Your solution:
Confidence rating:
Given Solution:
Self-critique (if necessary):
Self-critique rating:
Question:
`q006. Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Your solution:
Confidence rating:
Given Solution: The red lead of the generator has a direct connection through the white and red wires to the positive lead of the generator, and through the green and black wires to the negative generator lead.
Removing the leads will not prevent current from flowing.
Self-critique (if necessary):
Self-critique rating:
Question:
`q007. The red lead of the meter is now connected to the white lead.
Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Your solution:
Confidence rating:
Given Solution: The red lead of the meter has a direct path through the white and red wires to the positive generator lead. Current through the black meter lead must also pass through the second bulb, so that lead is not directly connected to the generator.
If the black lead is removed, the circuit through the second bulb will be broken. That bulb will have no connection, direct or indirect, to the positive generator lead. The first bulb will remain connected to the generator and current will flow through it.
Self-critique (if necessary):
Self-critique rating:
Question:
`q008. Trace the flow of current through the circuit below.
Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Your solution:
Confidence rating:
Given Solution:
The red lead of the meter has a direct connection through the red wire to the positive generator lead. The black lead of the meter is connected to the white wire, which is connected to the bulb. Current through the white wire can get to the negative generator lead, but only by passing through the bulb. So the meter is not directly connected to the generator.
Current can flow from the positive generator lead through the red wire, the first bulb and the black wire to the negative generator lead. Current can alternatively flow from the positive generator lead through the red wire, through the meter, through the black wire, through the second bulb, through the green wire and the black wire to the negative generator terminal.
Removing the meter leads will break the circuit through the second bulb. The first bulb will remain connected to the generator and current will still flow through it.
Self-critique (if necessary):
Self-critique rating:
Question:
`q009. Trace the flow of current through the circuit below.
Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Your solution:
Confidence rating:
Given Solution:
The red lead of the meter is connected to the negative lead of the generator (which is usually a bad idea). The black lead of the meter has direct connections through the black and green wires to the bulbs. So it is possible for current to flow from the positive side of the circuit (red and white wires, both directly connected to positive generator lead) to the negative side (green and black wires) then through the meter to the negative generator lead.
The current must pass through the meter in order to flow into the negative generator lead. If either meter lead is disconnected the current flow will cease.
Self-critique (if necessary):
Self-critique rating:
Question:
`q010. Trace the flow of current through the circuit below. The meter leads are connected on different sides of the top bulb.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Your solution:
Confidence rating:
Given Solution:
The positive generator lead has direct connections to the bulb nearest the meter, and to the black meter lead (generally a bad idea).
The negative generator lead a direct connection to the other bulb.
There are two possible paths through the circuit, one passing through both bulbs, and another through the meter and the bulb in the middle. These paths branch at the top bulb, with part of the current going through that bulb and part through the meter.
If the leads of the meter are removed, the first path remains unbroken and current will flow.
Self-critique (if necessary):
Self-critique rating:
Question:
`q011. Trace the flow of current through the circuit below. The red meter lead is connected on the left side of the lower bulb.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Will current flow through the meter?
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Your solution:
Confidence rating:
Given Solution: There is an unbroken circuit passing directly through both bulbs. The current does have an alternative between flowing through the green wire and the meter. The wire has negligible resistance to the flow of current, while the meter does have some resistance to current flow (perhaps a very large resistance), so all the current will take the path of lesser resistance and flow through the green wire. The meter will have no effect at all on the circuit.
Self-critique (if necessary):
Self-critique rating:
Question:
`q012. Trace the flow of current through the circuit below. The red meter lead is connected on the right side of the lower bulb.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Will current flow through the meter?
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Your solution:
Confidence rating:
Given Solution:
The red lead of the meter has a direct connection through the black wire to the negative generator lead (probably a bad idea). The black meter lead has a bulb between it and the positive terminal of the generator, so the meter does not have a direct connection to the generator.
Removing the leads of the meter will not break the circuit, so current will still flow.
The current has the choice of flowing through the meter or through the bulb in the middle. That bulb does have resistance to the flow of current, so if the meter is connected as shown, some current will flow through it.
Self-critique (if necessary):
Self-critique rating:
Question:
`q013. Trace the flow of current through the circuit below.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Will current flow through the meter?
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Your solution:
Confidence rating:
Given Solution:
The red lead of the meter has a direct connection to the positive terminal of the generator, through the red wire. The black meter lead has a bulb between it and the negative terminal of the generator so the meter is not directly connected to the generator.
Removing the meter will not break this path, so current will still flow through the bulbs.
The circuit has an unbroken path from the positive generator lead through one bulb then the other to the negative generator lead. Current has a choice of flowing through the meter or through the top bulb; since that bulb has resistance to current flow, some current will flow through the meter.
Self-critique (if necessary):
Self-critique rating:
Question:
`q014. Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If one lead is detached from the capacitor, will current flow?
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If one lead is detached from the bulb, will current flow?
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Your solution:
Confidence rating:
Given Solution: The current will flow from the positive lead through the capacitor then the second bulb and to the negative generator lead.
The capacitor is between the bulb and the positive generator lead, while the bulb is between the capacitor and the negative generator lead, so neither has a direct connection to the generator.
If either lead is detached from the capacitor, the circuit will be broken and no current will flow.
If either lead is detached from the bulb, the circuit will be broken and no current will flow.
Self-critique (if necessary):
Self-critique rating:
Question:
`q015. Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If one lead is detached from the capacitor, will current flow?
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If one lead is detached from the bulb, will current flow?
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Your solution:
Confidence rating:
Given Solution:
Current can flow from the positive generator lead through the red wire, the bulb and the black wire to the negative generator lead.
However the path through the white wire, the generator and the green wire ends up where it started, so there is no current through the capacitor.
If a lead is detached from the capacitor the circuit the circuit through the bulb remains. Since there was no current through the capacitor, disconnecting one of these leads has no effect.
If a lead is detached from the bulb the circuit through the bulb is broken. There will still be no current through the capacitor.
Self-critique (if necessary):
Self-critique rating:
Question:
`q016. Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If one lead is detached from the capacitor, will current flow?
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If one lead is detached from the bulb, will current flow?
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Your solution:
Confidence rating:
Given Solution:
Current can flow from the positive generator lead through the red wire, the bulb and the black wire to the negative generator lead, or from the positive generator lead through the red wire, the white wire, the capacitor, the green wire and the black wire to the negative generator lead. The current branches at the bulb, some taking one path and some the other.
If a lead is detached from the capacitor the circuit through the capacitor is broken, but the circuit through the bulb remains.
If a lead is detached from the bulb the circuit through the bulb is broken, but the circuit through the capacitor remains.
Self-critique (if necessary):
Self-critique rating:
Question:
`q017. Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If the white lead is detached from the capacitor, will current flow?
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If the green lead is detached from the bulb, will current flow?
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Your solution:
Confidence rating:
Given Solution:
The bulb has a direct connection to the generator, through the red and black wires.
The capacitor has a direct connection to the generator, through the red and white wires on the positive side, through the green and black wires on the negative side.
However there is a direct connection between the positive and negative generator terminals, through the red, yellow, green and black wires. This path has practically no resistance to the flow of current, so all the current that flows will be through this path, and neither the bulb nor the capacitor will carry any current. This path is called a 'short circuit'. If the voltage source has very low resistance to the flow of current (not the case for this generator), a very large current will flow, melting the wires.
Self-critique (if necessary):
Self-critique rating:
Question:
`q018. Trace the flow of current through the circuit below. Note the battery between the 'red' side of the bulb and the white lead.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red is detached from the bulb, will current flow?
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Your solution:
Confidence rating:
Given Solution:
The yellow lead still provides a direct path between the positive and negative leads of the generator, so no current from the generator will flow through the bulb or the capacitor.
The capacitor is directly connected to the positive terminal of the battery by the white wire, and by the yellow wire to the negative battery terminal, so current will flow through the capacitor (at least for a time, as we will see later).
Self-critique (if necessary):
Self-critique rating:
Question:
`q019. Trace the flow of current through the circuit below. Note the yellow lead has been removed.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red lead is detached from the bulb, will current flow?
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Your solution:
Confidence rating:
Given Solution:
The bulb has a direct connection to the generator, but not to the battery (the capacitor intervenes between the battery and the bulb).
The battery lies between the positive generator lead and the capacitor, which is therefore not directly connected to the generator.
The bulb is between the capacitor and the battery, so the capacitor is not directly connected to the battery.
Detaching the white lead will break both the connection of the capacitor with the positive terminals of both the generator and the battery, so no current will flow through the capacitor. However the generator will still be directly connected to the bulb, through which current will therefore flow.
Detaching the red lead will isolate the positive generator terminal, breaking any circuit through the generator. However an unbranching circuit will remain through the battery, the bulb and the capacitor.
Self-critique (if necessary):
Self-critique rating:
Question:
`q020. Trace the flow of current through the circuit below. Note that the yellow lead has been reintroduced, but in a different place.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red is detached from the bulb, will current flow?
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The battery is directly connected by the red lead to the positive lead of the generator, and by the yellow lead to the negative generator lead. So it is possible for current to flow directly from generator through battery and back to the generator, without passing through any other circuit element.
The bulb in the middle also has a direct connection to the generator, through the red lead and the black lead.
From the battery the current can flow from the positive terminal of the battery through the white wire, the capacitor, the green wire and the bulb back to the negative terminal of the generator.
If either end of the white lead is detached, the positive terminal of the battery will become detached from the circuit, interrupting two of the three possible paths through the circuit and leaving only the path from generator through bulb and back through generator.
If either end of the red lead is detached, the positive lead of the generator will be detached from the circuit so no current can flow through the generator. The circuit from battery through capacitor through bulb will remain.
Your solution:
Confidence rating:
Given Solution:
Self-critique (if necessary):
Self-critique rating:
Question:
`q021. Trace the flow of current through the circuit below. Note the yellow lead has been moved once more.
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Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red is detached from the bulb, will current flow?
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It is possible for current to flow from generator through bulb and back to generator.
The battery is directly connected to the generator through the red lead on the positive generator lead, and through the yellow, green and black leads to the negative generator lead.
The capacitor is attached through the white and yellow leads to the positive terminal of the battery, so both terminals of the capacitor will remain at the voltage of that terminal and no current will flow through the capacitor. The capacitor does not have a direct connection to the negative terminal of the battery.
It is also possible for current to flow from the positive terminal of the battery, through the yellow and green wires to the bulb, and through the bulb to the negative terminal of the battery.
There is a path from the positive lead of the generator to the negative terminal of the battery, through the battery, through the white wire to the capacitor, through the green wire to the black wire, and through it to the negative generator lead. However the yellow wire and white wires connected to the positive battery terminal prevent current from flowing through the capacitor.
Your solution:
Confidence rating:
Given Solution:
Self-critique (if necessary):
Self-critique rating:
If the meter allows current to flow easily, will disconnecting the meter make a difference in the flow of current through the bulbs?
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If the meter has a high resistance to the flow of current, will disconnecting the meter make a difference in the flow of current through the bulbs?
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110328 Physics II
There are additional notes, ready to insert, but they're in color and it won't help to print them. We'll display some of the originals, in full size, in class.
Questions left from last class:
`q004. A magnet spins at 10 revolutions per second in the vicinity of a coil of wire enclosing a total area of 1000 cm^2. The magnet creates a maximum field of .04 Tesla within that area. At what average rate is the magnetic flux through the coil changing?
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`q005. Charge Q creates electrostatic flux 4 pi k Q, with k = 9 * 10^9 N m^2 / Coulomb^2. A 5 meter length of wire contains a uniformly distributed charge of 8 microCoulombs.
How much charge does a 25 cm length of the wire contain?
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What will therefore be the electrostatic flux through a piece of pipe 25 cm long, which surrounds the wire?
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If the diameter of the pipe is 5 cm, then how much flux is there per square centimeter of the pipe?
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How much is that per square meter?
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`q006. Suppose the blackboard is uniformly covered by electrostatic charge, with a total charge of 60 microCoulombs. We place a piece of tile 1 cm from the board, parallel to and near the center of the board. The tile dimensions are 15 cm by 15 cm. The tile does not affect the electric field, which effectively passes right through it.
What must be the direction of the electric field relative to the surface of the tile?
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What do you think is the electrostatic flux through the tile?
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What is the electrostatic flux per square centimeter, and per square meter of the tile surface?
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How much do you think this result will change if we move the tile 2 cm further from the board?
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`q007. A current of .25 amps is driven by a 1.5 volt battery through a 100-turn coil of radius 2 cm.
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What magnetic field results at the center of the coil?
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What therefore is the magnetic flux within the coil?
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If the battery is removed the current in the coil will quickly fall to zero. If this occurs in 20 milliseconds, then at what average rate must the magnetic flux change?
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To measure voltage the meter needs to be connected in parallel across the appropriate element in the circuit.
The voltmeter has very high resistance. Connected in parallel it draws very little current and has very little effect on the behavior of the circuit itself.
The ammeter has very low resistance. If it is connected in parallel with a voltage source, a large current will flow through the ammeter. This both disrupts the circuit and destroys the ammeter. If disconnecting the ammeter doesn't interrupt the circuit, then you almost certainly have the ammeter in parallel with something. This is to be avoided at all costs.
Below the ammeter is in series with the circuit. As long as the current flowing in the circuit is small enough to be measured by the meter, this will be safe. The ammeter should not significantly disrupt the circuit if it is connected in series. However for low-resistance circuits the resistance of the ammeter does have to be considered.
When asked to measure the current and voltage in the circuit, one group came up with an interesting variation.
You should consider what the voltage and current measured in this setup tell us.
The circuit below would measure the voltage across the source and across the resistance, as well as across the ammeter.
If we trace a loop around the circuit, some voltage changes will be positive and some negative. Since we end up where we started, the sum of the voltage changes is zero.
You should have a table of voltage vs. current across the bulb. From these measurements you will be able to determine resistance vs. current.
Additional questions.
The leads from the generator are sort of silver-colored. They run out of the generator, and appear again at the bottom of the picture, where they are connected to the red and black leads.
Assume that, when the meter is cranked counterclockwise, the lead connected to the red lead is positive and the lead connected to the black lead is negative.
Trace the current from the generator through the circuit and back to the generator.
Does the current pass through the bulb?
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Trace the current in this circuit.
Does current pass through both bulbs?
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If one bulb was disconnected, would current still flow?
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Is there a direct connection between the first bulb and the generator? A direct connection is one in which you can get from one side of the bulb to one terminal of the generator without passing through another bulb, and from the opposite side of the bulb to the opposite terminal of the generator.
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Is there a direct connection between the second bulb and the generator?
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Now trace the current in this circuit.
Does current pass through both bulbs?
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Is it possible to disconnect one bulb, but have the current still flow through the other?
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Is there a direct connection between the first bulb and the generator?
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Is there a direct connection between the second bulb and the generator?
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Now there's a meter in the circuit. The red lead of the meter is connected to the 'red' side of the bulb, the black lead to the 'black' side.
Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through the bulb?
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Does the meter now have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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The red lead of the meter is now connected to the white lead.
Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Trace the flow of current through the circuit below.
Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Trace the flow of current through the circuit below.
Does the meter have a direct connection to the generator?
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If the leads of the meter are removed, will current still flow through both bulbs?
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Trace the flow of current through the circuit below. The meter leads are connected on different sides of the top bulb.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Trace the flow of current through the circuit below. The red meter lead is connected on the left side of the lower bulb.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Will current flow through the meter?
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Trace the flow of current through the circuit below. The red meter lead is connected on the right side of the lower bulb.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Will current flow through the meter?
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Trace the flow of current through the circuit below.
Does the meter have a direct connection to the generator?
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Which bulb or bulbs will carry a current?
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If the leads of the meter are removed, will current still flow?
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Will current flow through the meter?
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Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If one lead is detached from the capacitor, will current flow?
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If one lead is detached from the bulb, will current flow?
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Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If one lead is detached from the capacitor, will current flow?
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If one lead is detached from the bulb, will current flow?
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Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If one lead is detached from the capacitor, will current flow?
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If one lead is detached from the bulb, will current flow?
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Trace the flow of current through the circuit below.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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If the white lead is detached from the capacitor, will current flow?
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If the green lead is detached from the bulb, will current flow?
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Trace the flow of current through the circuit below. Note the battery between the 'red' side of the bulb and the white lead.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red is detached from the bulb, will current flow?
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Trace the flow of current through the circuit below. Note the yellow lead has been removed.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red is detached from the bulb, will current flow?
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Trace the flow of current through the circuit below. Note that the yellow lead has been reintroduced, but in a different place.
Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red is detached from the bulb, will current flow?
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Trace the flow of current through the circuit below. Note the yellow lead has been moved once more.
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Does the bulb have a direct connection to the generator?
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Does the capacitor have a direct connection to the generator?
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Does the bulb have a direct connection to the battery?
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Does the capacitor have a direct connection to the battery?
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If the white lead is detached from the capacitor, will current flow?
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If the red is detached from the bulb, will current flow?
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