Page 39 - Physics - XII

Q4. A galvanometer of 100 Ω resistance gives full scale defl ection for 10 mA current. To use it as
an ammeter of 10 A range, the resistance of the shunt required is

(a) 10 Ω (b) 0.10 Ω (c) 0.01 Ω (d) 0.001 Ω
Q5. An ammeter gives full scale defl ection when current of 1.0 A is passed in it. It is converted into
a 100 A range ammeter, what will be the ratio of the shunt resistance and its resistance?
(a) 1 : 9 (b) 9 : 1 (c) 1 : 11 (d) 11 : 1
Q6. A galvanometer can be converted into a voltmeter by connecting a

(a) high resistance in series (b) high resistance in parallel
(c) low resistance in parallel (d) low resistance in series
Q7. The pole pieces of the magnet used in a pivoted coil galvanometer are

(a) plane surfaces of a horse-shoe magnet. (b) cylindrical surfaces of a bar magnet.
(c) plane surfaces of a bar magnet. (d) cylindrical surfaces of a horse-shoe magnet.
Q8. The sensitivity of a moving coil galvanometer can be increased by decreasing
(a) the number of turns in the coil. (b) the area of the coil.

(c) the magnetic fi eld. (d) the couple per unit twist of the suspension.
Q9. The reason the coil is bound over the metallic frame in moving coil galvanometer is
(a) the metallic frame helps in oscillation.

(b) the metallic frame helps in making steady defl ection without any oscillation.
(c) the metallic frame increases the magnetic fi eld.
(d) none of these.
Q10. To convert a galvanometer into an ammeter, one should connect

(a) high resistance in series with galvanometer. (b) low resistance in series with galvanometer.
(c) low resistance in parallel with galvanometer. (d) high resistance in parallel with galvanometer.

Answer key
1. (a), 2. (d), 3. (a), 4. (b), 5. (a), 6. (a), 7. (d), 8. (d), 9. (b), 10. (c)

Case Study-based Questions

Read the paragraph and answer the questions that follow.
Moving coil galvanometer operates on Permanent Magnet Moving Coll (PMMC) mechanism and was

designed by the scientist D'arsonval. Moving coil galvanometers are of two types
(i) Suspended coil (ii) Pivoted coil type or tangent galvanometer

Its working is based on the fact that when a current carrying coil is placed in a magnetic fi eld, it experiences
a torque. This torque tends to rotate the coil about its axis of suspension in such a way that the magnetic
fl ux passing through the coil is maximum.
Q1. A moving coil galvanometer is an instrument which

(a) is used to measure e.m.f. (b) is used to measure potential diff erence.
(c) is used to measure resistance.
(d) is a defl ection instrument which gives a defl ection when a current fl ows through its coil.

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