course Phy 202 ?????}o??????{???assignment #004004.
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10:29:49 Query introductory set #1, 10-17 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 --> The potential difference in volts between two different points on the x axis due to a charge at the origin can be found by performing a couple of steps. 1. First the force exerted on the points by the charge at the origin must be found. 2. Then the work can be calculate using W = F*d 3. Finally the potential difference can be found using W = Q*Vba confidence assessment: 2
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10:32:33 07-28-2007 10:32:33 ** 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 w ""ork, 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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NOTES -------> Multiply average force on a Coulomb of charge by displacement from the first point to the second. Find the force on 1 Coulomb at each of the two points and average the forces. Force * displacement = potential difference. This approximation becomes more accurate using smaller intervals on the line, calculating the work done over each, and adding them up.
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10:41:10 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 gradient is equal to the electric field strength. confidence assessment: 2
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10:42:17 ** 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 --> Oh, I guess I got my terms confused. V = E * dr self critique assessment: 2
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10:45:14 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 --> The formula E = F/q can be used to find the average electric field between two points after force has been calculated using W = F*d (---> F = W/d) confidence assessment: 2
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10:46:37 ** 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 --> I got it right but I'm not clear on the notation. Does 'd have to be used in the formulas? And what does s stand for? self critique assessment: 3
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10:50:28 In your own words explain the meaning of voltage.
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RESPONSE --> Voltage is the amount of work performed on each Coulomb of the charge to move it through the potential difference between two points due to the electic field. confidence assessment: 2
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10:50:35 ** Voltage is the work done per unit of charge in moving charge from one point to another. **
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RESPONSE --> self critique assessment: 3
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