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Moving Charges And Magnetism
Question
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A galvanometer having a coil resistance of 100 Ω gives a full-scale deflection, when a current of 1 mA is passed through it. The value of the resistance, which can convert this galvanometer into ammeter giving a full-scale deflection for a current of 10 A, is:

  • 0.01 Ω

  • 2 Ω

  • 0.1 Ω

  • 3 Ω

Answer

A.

0.01 Ω

Maximum voltage that can be applied across the galvanometer coil = 100 Ω x 10-3 A = 0.1


If Rs is the shunt resistance, then
Rs x 10 A = 0.1 V
Rs = 0.01 Ω

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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.