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Moving Charges And Magnetism

Question
CBSEENPH12039984
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A galvanometer has a coil of resistance 100 Ω and gives a full-scale deflection for 30 mA current. If it is to work as a voltmeter of 30 V range, the resistance required to be added will be

  • 900 Ω

  • 1800

  • 500 Ω

  • 1000 Ω

Solution

A.

900 Ω

Required resistance
straight R space equals space straight V over straight i subscript straight g minus space straight G equals space fraction numerator 30 over denominator 30 space straight x space 10 to the power of negative 3 end exponent end fraction space minus space 100 space equals space 900 space straight capital omega

Some More Questions From Moving Charges And Magnetism Chapter

Two moving coil meters, M1 and M2 have the following particulars:
R1 = 10 Ω   N1 = 30,
A1 = 3.6 x 10–3 m2,  B1 = 0.25 T
R2 = 14 Ω;  N2 = 42,
A2 = 1.8 x 10–3 m2, B2 = 0.50 T
(The spring constants k are identical for the two meters).
Determine the ratio of (a) current sensitivity and (b) voltage sensitivity of M2 and M1.

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