A potentiometer wire of length 10 m has a total resistance of 20 Ω. It is connected in series with a 480 Ω external resistor and a stable 2.0 V battery of negligible internal resistance. What is the potential gradient (k) along the potentiometer wire?

Answer and explanation

Correct answer: C. 0.008 V/m (8.0 mV/m)

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  1. Step 1: Total circuit resistance is: .
  2. Step 2: Circuit current is: .
  3. Step 3: Potential drop across the 10 m potentiometer wire is: .
  4. Step 4: Potential gradient () is the potential drop per unit length:
Answer
0.008 V/m (8.0 mV/m)
Why not the others: '0.2 V/m' assumes the entire 2.0 V drops across the wire without the 480 ohm resistor; '0.08 V/m' forgets to divide by the 10 m wire length; '0.002 V/m' miscalculates current.

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