110328 Physics II

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course PHY 242

3/31/11; 15:30The pics did not up-load, but they are in order with the 21 pictures. If you wish for me to draw the schematics i will be happy to just let me know!

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?

`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?

What will therefore be the electrostatic flux through a piece of pipe 25 cm long, which surrounds the wire?

If the diameter of the pipe is 5 cm, then how much flux is there per square centimeter of the pipe?

How much is that per square meter?

`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?

What do you think is the electrostatic flux through the tile?

What is the electrostatic flux per square centimeter, and per square meter of the tile surface?

How much do you think this result will change if we move the tile 2 cm further from the board?

`q007. A current of .25 amps is driven by a 1.5 volt battery through a 100-turn coil of radius 2 cm.

What magnetic field results at the center of the coil?

What therefore is the magnetic flux within the coil?

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?

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.

1

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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Yes

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2

Trace the current in this circuit.

Does current pass through both bulbs?

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yes

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If one bulb was disconnected, would current still flow?

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no

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Is there a direct connection between the first bulb and the generator?

****no

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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.

Is there a direct connection between the second bulb and the generator?

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No

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3

Now trace the current in this circuit.

Does current pass through both bulbs?

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Yes

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Is it possible to disconnect one bulb, but have the current still flow through the other?

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Yes, providing the other wire is still connected

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Is there a direct connection between the first bulb and the generator?

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Yes

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Is there a direct connection between the second bulb and the generator?

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Yes

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4

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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Yes

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If the leads of the meter are removed, will current still flow through the bulb?

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Yes

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5

Does the meter now have a direct connection to the generator?

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No

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If the leads of the meter are removed, will current still flow through both bulbs?

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Yes, providing that is all that is moved.

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6

Does the meter have a direct connection to the generator?

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Yes, the current can travel though the meter and straight back 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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yes

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7

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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No

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If the leads of the meter are removed, will current still flow through both bulbs?

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No, the lower bulb yes but the higher bulb would not illuminate

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8

Trace the flow of current through the circuit below.

Does the meter have a direct connection to the generator?

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No, it is in series with the second bulb in the circuit.

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If the leads of the meter are removed, will current still flow through both bulbs?

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No, again it is in series with the bulb.

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9

Trace the flow of current through the circuit below.

Does the meter have a direct connection to the generator?

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No, the current must flow through the bulbs

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If the leads of the meter are removed, will current still flow through both bulbs?

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No the circuit is not closed, though the current would pass through the bulbs there would not be any power.

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10

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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No

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Which bulb or bulbs will carry a current if the volt meter is removed?

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Both will!

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If the leads of the meter are removed, will current still flow?

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Yes

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11

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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no

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Which bulb or bulbs will carry a current?

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Both

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If the leads of the meter are removed, will current still flow?

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yes

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Will current flow through the meter?

Not if it is removed from the circuit.

If it is in the circuit then still no, the wire has less resistance than the meter if it is on the amp meter, I believe.

If it is on the volt setting then yes it might carry some of the current.

12

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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No

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Which bulb or bulbs will carry a current?

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The second one only, providing the meter is on bc.

the bulbs are in series with the generator; if the meter has very low resistance current won't flow through the second bulb but will flow through the first in any case

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If the leads of the meter are removed, will current still flow?

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Yes! In fact both lights will illuminate then for sure.

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Will current flow through the meter?

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Not if it is unhooked or off. Otherwise, the current will only flow through the meter and not through the bulb.

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13

Trace the flow of current through the circuit below.

Does the meter have a direct connection to the generator?

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No

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Which bulb or bulbs will carry a current?

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The second for sure but the first will not if the meter is on- less resistance.

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If the leads of the meter are removed, will current still flow?

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Yes

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Will current flow through the meter?

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Not if it is out of the circuit, or if it is off.

But if it is on then it will read the meter and not illuminate the bulb.

if it's on volts then it will draw very little current and both bulbs will light

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14

Trace the flow of current through the circuit below.

Does the bulb have a direct connection to the generator?

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No

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Does the capacitor have a direct connection to the generator?

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No

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If one lead is detached from the capacitor, will current flow?

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No

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If one lead is detached from the bulb, will current flow?

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No

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15

Trace the flow of current through the circuit below.

Does the bulb have a direct connection to the generator?

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Yes

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Does the capacitor have a direct connection to the generator?

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No

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If one lead is detached from the capacitor, will current flow?

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Yes, through the bulb, but not the capacitor.

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If one lead is detached from the bulb, will current flow?

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Not in the case of the black lead or the red one, in any other case yes it will flow through the bulb.

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16

Trace the flow of current through the circuit below.

Does the bulb have a direct connection to the generator?

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Yes

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Does the capacitor have a direct connection to the generator?

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Yes

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If one lead is detached from the capacitor, will current flow?

Yes but only through the bulb!

If one lead is detached from the bulb, will current flow?

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If the red or black lead is disconnected, no current will flow through the circuit.

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17

Trace the flow of current through the circuit below.

Does the bulb have a direct connection to the generator?

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Yes

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Does the capacitor have a direct connection to the generator?

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Yes

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If the white lead is detached from the capacitor, will current flow?

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No

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If the green lead is detached from the bulb, will current flow?

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Yes

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If the green lead is detached from the bulb, current will flow through the bulb, but not through the capacitor.

However current won't flow through the capacitor in any case, since both of its terminals are connected to the same generator lead.

18

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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Yes

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Does the capacitor have a direct connection to the generator?

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No

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Does the bulb have a direct connection to the battery?

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No

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Does the capacitor have a direct connection to the battery?

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Yes

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If the white lead is detached from the capacitor, will current flow?

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Yes, but only through the bulb

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If the red is detached from the bulb, will current flow?

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Yes, but not through the generator.

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19

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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Yes!

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Does the capacitor have a direct connection to the generator?

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No

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Does the bulb have a direct connection to the battery?

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No

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Does the capacitor have a direct connection to the battery?

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No

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If the white lead is detached from the capacitor, will current flow?

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Only through the bulb.

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If the red is detached from the bulb, will current flow?

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Yes, but only via the battery.

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20

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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Yes

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Does the capacitor have a direct connection to the generator?

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No

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Does the bulb have a direct connection to the battery?

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Yes, but it is directionally challenged by the flow of current.

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Does the capacitor have a direct connection to the battery?

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No

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If the white lead is detached from the capacitor, will current flow?

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Yes, but not to the capacitor.

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If the red is detached from the bulb, will current flow?

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Yes, but the generator will not be in the circuit.

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21

Trace the flow of current through the circuit below. Note the yellow lead has been moved once more.

Does the bulb have a direct connection to the generator?

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Yes

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Does the capacitor have a direct connection to the generator?

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No

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Does the bulb have a direct connection to the battery?

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Yes

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Does the capacitor have a direct connection to the battery?

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No, the leads are both on the positive side of the battery.

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If the white lead is detached from the capacitor, will current flow?

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Yes, but not to the capacitor.

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If the red is detached from the bulb, will current flow?

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Yes, but not through the generator!

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&#Your work looks good. See my notes. Let me know if you have any questions. &#