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1. Four point charges are placed at the corners of a square as shown in the figu

ID: 1426760 • Letter: 1

Question

1. Four point charges are placed at the corners of a square as shown in the figure. Each side of the square has length 2.0 m. Determine the electric potential at the point P, the center of the square, if we set V = 0 (ground) to be an infinite distance from the charges. Hint: Potentials at the center of configurations like this can be very large, due to the proximity of the field charges and the way we defined ground (V= 0 at infinity). ?

2. If a +1 nC charge were placed at this point, what would be its potential energy relative to ground?

3. If a -2 nC charge were placed at this point, what would be its potential energy relative to ground?

+4 HC C

Explanation / Answer

Distance to the centre from any corner = sq.root of 2 = 1.414

Electric potential at P = kQ1/r + kQ2/r + kQ3/r + kQ4/r = k/r ( 4-3+1+4) = 54* 10 ^ 9 * 10 ^-6 / 1.414

= 38.1837 * 10^ 3 V

Potential Energy for 1 nC= kQq/r = 38.1837 * 10^ 3 *1 nano = 38.1837 *10^-6 J

Potential Energy for -2 nC= kQq/r = 38.1837 * 10^ 3 *-2 nano = - 76.367 *10^-6J