course PHY202
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11:40:04 Query introductory set #1, 9-16 Explain how to find the potential difference in volts between two given points on the x axis, due to a given charge at the origin.
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RESPONSE --> When a charge moves from a point at potential V1 to a point at potential V2, it passes through a potential difference dV = V2-V1.
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11:40:44 ** Potential difference is the work per Coulomb of charge moved between the two points. To find this work you can multiply the average force on a Coulomb of charge by the displacement from the first point to the second. You can find an approximate average force by finding the force on a 1 Coulomb test charge at the two points and averaging the two forces. Multiplying this ave force by the displacement gives an approximate potential difference. Since the force is not a linear function of distance from the given charge, if the ratio of the two distances from the test charge is not small the approximation won't be particularly good. The approximation can be improved to any desired level of accuracy by partitioning the displacement between charges into smaller intervals of displacement and calculating the work done over each. The total work required is found by adding up the contributions from all the subintervals. University Physics students should understand how this process yields the exact work, which is the integral of the force function F(x) = k Q / x^2 between the two x values, yielding total work W = k * Q * 1 Coulomb ( 1 / x1 - 1 / x2) and potential difference V = k * Q ( 1 / x1 - 1 / x2). **
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RESPONSE --> Ok. W = Q x dV
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11:45:51 Explain how to find the potential difference between two points given the magnitude and direction of the uniform electric field between those points.
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RESPONSE --> The potential difference is the product of the potential gradient and the displacement.: dV = Dv/dx*ds The work done on the charge is therefore dW = qdV; this work in the product dW = Fave*ds of the displacement and the average force on the charge. Setting these two expressions for workdW equal we arrive at the conclusion that Fave = qdV/dx = qE
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11:45:59 ** The work per Coulomb done between the two points is equal to the product of the electric field E and the displacement `dr. Thus for constant field E we have V = E * `dr. **
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RESPONSE -->
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11:47:54 Explain how to find the average electric field between two points given a specific charge and the work done on the charge by the electric field as the charge moves between the points.
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RESPONSE --> E = dV/Q
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11:48:07 ** You get ave force from work and distance: F_ave = `dW / `ds. You get ave electric field from work and charge: E_ave = F / q. An alternative: Find potential difference `dV = `dW / q. Ave electric field is Eave = `dV / `ds **
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RESPONSE --> ok
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11:49:22 In your own words explain the meaning of the electric field.
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RESPONSE --> Electirc field extends outward form every charge and permeates all of space.
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11:49:34 STUDENT RESPONSE AND INSTRUCTOR COMMENT: electric field is the concentration of the electrical force ** That's a pretty good way to put it. Very specifically electric field measures the magnitude and direction of the electrical force, per unit of charge, that would be experienced by a charge placed at a given point. **
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RESPONSE --> ok
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11:50:13 In your own words explain the meaning of voltage.
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RESPONSE --> Potential difference.
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11:50:19 ** Voltage is the work done per unit of charge in moving charge from one point to another. **
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RESPONSE --> ok
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xnC癸ԁ}ᶢ assignment # ƷOpDظ Physics II 03-26-2006 g͂жцٹ_aۍ assignment #022 ƷOpDظ Physics II 03-26-2006 "