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A wire of length 4 m and resistance 8 ohm is connected in series with a 2 V battery (internal resistance 1 ohm) and a 7 ohm resistor. Find the potential gradient (potential drop per unit length) along the wire.

1. 0.25 V/m
2. 0.50 V/m
3. 0.75 V/m
4. 1.00 V/m

Correct answer: 0.25 V/m

Solution

Total resistance = 8 + 7 + 1 = 16 ohm, current = 2/16 = 0.125 A. Drop across the wire = 0.125 * 8 = 1 V; gradient = 1 V / 4 m = 0.25 V/m.

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