course Phy 232 x}jԛNjҒassignment #004
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20:13:46 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 is the difference of potentials at the points on the x-axis. These potentials are Work /Coulomb. The potential at each point can be found by taking the force at each point due to the charge multiplied by the distance from the charge and divide that by the amount of charge. confidence assessment: 2
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20:17:29 ** 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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RESPONSE --> Yes, the integral of the force function between the two values would give a more accurate answer. self critique assessment: 2
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20:29:19 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 electric field is in F/C. Multiply this by 1C from a 1C test charge to get the Force. This force is acting between the two points to do work F * `ds. The work is divided by the amount of charge. The direction of the field determines the Force acting between the points and influences the work needed to move between the points. confidence assessment: 2
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20:32:53 ** 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 --> This makes sense that the electric field is measured in N/C and the displacement is in m. So it seems natural that Nm/C = J/C. self critique assessment: 2
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20:36:45 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 average electric field can be found by dividing the average force by the charge. The average force is found by dividing the work done by the distance between the points. confidence assessment: 3
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20:36:48 ** 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 --> self critique assessment: 3
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20:37:16 In your own words explain the meaning of voltage.
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RESPONSE --> Voltage is the measure of potential difference. It is the amount of work per coulomb needed to move to a point due to a charge. confidence assessment: 3
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20:37:18 ** 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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