The potentiometer wire PQ is 100 cm long and its resistance is 2r, where r is the internal resistance of the battery. PC is equal to:
Correct answer: B. 75cm
- A. 25cm
- B. 75cm
- C. 50cm
- D. 40cm
Explanation
The potential gradient in the wire PQ is two‑thirds of the emf E divided by the length 100 cm. At balance, the emf E/2 equals the potential drop across PC, soE/2 = (2E/3) * (PC/100).Solving for PC givesPC = (E/2) * (100 * 3)/(2E) = 75 cm.
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About Current Electricity
Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.
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