Moving Charges and Magnetism - Result Question 79
81. A galvanometer having a coil resistance of 60 $\Omega$ shows full scale deflection when a current of $1.0 amp$ passes through it. It can be converted into an ammeter to read currents upto $5.0 amp$ by
(a) putting in series a resistance of $15 \Omega$
(b) putting in series a resistance of $240 \Omega$
(c) putting in parallel a resistance of $15 \Omega$
(d) putting in parallel a resistance of $240 \Omega$
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Answer:
Correct Answer: 81. (c)
Solution:
- (c) $G=60 \Omega, I_g=1.0 A, I=5 A$.
Let $S$ be the shunt resistance connected in parallel to galvanometer $I_g G=(I-I_g) S$,
$S=\frac{I_g G}{I-I_g}=\frac{1}{5-1} \times 60=15 \Omega$
Thus by putting $15 \Omega$ in parallel, the galvanometer can be converted into an ammeter.
