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The electric potential V varies with distance x from a fixed point as follows: V = 5 V for 0 <= x < 10 m, then V decreases linearly from 5 V at x = 10 m to -10 V at x = 20 m. The electric field at x = 13 m is:
- (A) 7.5 V/m
- (B) -7.5 V/m
- (C) 1.5 V/m
- (D) -1.5 V/m
Correct answer: (C) 1.5 V/m
Solution
The original question references a V-x graph. The answer options -7.5 V/m and 7.5 V/m are the most commonly paired values in the standard version of this problem, where the slope in the region 10 < x < 20 m is (change in V)/(change in x) = (-10 - 5)/(20 - 10) = -15/10 = -1.5 V/m, so E = -(-1.5) = 1.5 V/m. However, many textbook versions of this exact problem yield E = -7.5 V/m, depending on the graph segment used. Since the graph is not available, the most defensible reconstruction gives 1.5 V/m.
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