Potentiometer — A/L Physics

How do I practise Potentiometer?

1 question with a worked solution

1. A potentiometer wire of length 100 cm and resistance 5.0 Ω is connected in series with a 4.0 V driver battery of negligible internal resistance and a series limiting resistor R_s = 15.0 Ω. What is the potential gradient along the potentiometer wire?
   1. A) 0.5 V m⁻¹ (0.005 V cm⁻¹)
   2. B) 2.0 V m⁻¹ (0.02 V cm⁻¹)
   3. C) 4.0 V m⁻¹ (0.04 V cm⁻¹)
   4. D) 1.0 V m⁻¹ (0.01 V cm⁻¹)
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   Correct answer: D) 1.0 V m⁻¹ (0.01 V cm⁻¹)

   Total circuit resistance R_total = R_wire + R_s = 5.0 Ω + 15.0 Ω = 20.0 Ω. Current in potentiometer wire I = V_driver / R_total = 4.0 V / 20.0 Ω = 0.20 A. Potential drop across the wire V_wire = I × R_wire = 0.20 A × 5.0 Ω = 1.0 V. Potential gradient k = V_wire / L = 1.0 V / 1.0 m = 1.0 V m⁻¹ (0.01 V cm⁻¹).

   Show worked solution

   Step 1: I = 4.0 V / (5.0 + 15.0) Ω = 0.20 A. Step 2: V_wire = I · R_wire = 0.20 A × 5.0 Ω = 1.0 V. Step 3: Potential gradient k = V_wire / L = 1.0 V / 1.0 m = 1.0 V m⁻¹. Answer: 1.0 V m⁻¹ (0.01 V cm⁻¹).
   Modelled on: the A/L Physics examination pattern

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Where does Potentiometer fit in the syllabus?

Unit 7.8 · Year 2 · Term 1