JEE Advanced · 2020 · 27 Sep 2020 · Paper 2 · Current Electricity

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In the balanced condition, the values of the resistances of the four arms of a Wheatstone bridge are shown in the figure below. The resistance

R_{3}

has temperature coefficient

0.0004° C^{- 1}

. If the temperature of

R_{3}

is increased by

100° C

, the voltage developed between S and T will be ____ volt.

Answer: 0.27

Solution

From the figure

R_{1} = 60 Ω, R_{2} = 100 Ω, R_{3} = 300 Ω, R_{4} = 500 Ω

with a

50

V supply. Heating

R_{3}

10 0^{\circ}

C gives

R_{3}^{'} = 300 (1 + 0.0004 \times 100) = 312 Ω

. The branch currents become

I_{1} = \frac{50}{372}

and

I_{2} = \frac{50}{600}

, so

V_{S} - V_{T} = 312 I_{1} - 500 I_{2} \approx 41.94 - 41.67 \approx 0.27

V. Official answer range 0.26–0.28 V.

JEE Advanced · 2020 · 27 Sep 2020 · Paper 2 · Numerical answer

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