Q61 / 90 · JEE Main 2019 (08 Apr Shift 2) · Physics

In the circuit shown, a four-wire potentiometer is made of a 400 cm long wire, which extends between A and B . The resistance per unit length of the potentiometer wire is r=0.01 Ω/cm. If an ideal voltmeter is connected as shown with jockey J  at 50 cm from end A , the expected reading of the voltmeter will be:
Figure

  • A
    0.50 V
  • Correct answer
    B
    0.25 V
  • C
    0.75 V
  • D
    0.20 V

Solution

From the given question we take, 

Current in the wire, I=VR=1.5+1.50.5+0.5+1+0.01×400=0.5 A

Resistance of 50 cm long wire, =50×0.01=0.5 Ω

Reading =  Current × Resistance
=0.5×0.5
=0.25 V

Hence, the correct answer is option: 'B'.

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