Current Electricity - Result Question 95

100. A potentiometer wire has length 4m and resistance 8Ω. The resistance that must be connected in series with the wire and an accumulator of e.m.f. 2V, so as to get a potential gradient 1mV per cm on the wire is

[2015]

(a) 40Ω

(b) 44Ω

(c) 48Ω

(d) 32Ω

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Answer:

Correct Answer: 100. (d)

Solution:

  1. (d) Total potential difference across potentiometer wire =103×400 volt =0.4 volt potential gradient =1mvcm

=103v/cm=101vm Let resistance of RΩ connected in series.

So, 2R+8=101×48=120

R+8=40 or, R=32Ω



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