A potentiometer wire of length 10 cm and resistance 32 Ω is connected in series with a battery of EMF 2 . 5 V , internal resistance 3 Ω and external resistance R . If a secondary cell of 0 . 4 V is ba

Question

A potentiometer wire of length 10 cm and resistance 32 Ω is connected in series with a battery of EMF 2 . 5 V , internal resistance 3 Ω and external resistance R . If a secondary cell of 0 . 4 V is balanced at 8 cm length. Then value of R is

TestHub · Accepted Answer

Potential gradient of potentiometer = 2.5 ( 3 + R + 32 ) × 30 10 Balancing length for cell of emf e = 0.4 V is 8 cm . ∴ 2.5 ( 35 + R ) × 3 × 8 = 0.4 ⇒ 5 × 3 × 4 = 0.04 × ( 35 + R ) 10 ⇒ 15 × 10 = 35 + R ⇒ R = 115 Ω

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