Page 40 - Physics - XII

Q2. To make the fi eld radial in a moving coil galvanometer
(a) number of turns of coil is kept small. (b) magnet is taken in the form of horse-shoe.
(c) poles are of very strong magnets. (d) poles are cylindrically cut.

Q3. To increase the current sensitivity of a moving coil galvanometer, we should decrease

(a) strength of magnet. (b) torsional constant of spring.
(c) number of turns in coil. (d) area of coil.
Answer key

1. (d), 2. (d), 3. (b)

Assertion-Reason Type Questions

These consist of two statements—Assertion (A) and Reason (R). Answer these questions by selecting
the appropriate option given below:
a. Both A and R are true and R is the correct explanation of A.

b. Both A and R are true and R is not the correct explanation of A.
c. A is true but R is false. d. A is false but R is true.

1. Assertion (A) : In moving coil galvanometer, the coil is would on a metallic frame.

Reason (R) : The metallic frame helps in making steady defl ection without oscillation.
2. Assertion (A) : Galvanometer to ammeter conversion takes place by connecting a low value
resistance in parallel with it.
Reason (R ) : The low value resistance increases the eff ective resistance and protects the
galvanometer.

3. Assertion (A) : Earth’s magnetic fi eld does not aff ect the functioning of a moving coil
galvanometer.
Reason (R) : Earth’s magnetic fi eld is too weak.

4. Assertion (A) : Galvanometer is used to measure polarity.
Reason (R) : Galvanometer is an instrument which is used to detect current in any circuit.
5. Assertion (A) : Out of galvanometer, voltmeter, and ammeter, resistance of ammeter is the
lowest and resistance of voltmeter is the highest.

Reason (R) : An ammeter is connected in series and a voltmeter is connected in parallel in a
circuit.
Answer key
1. (a), 2. (c), 3. (a), 4. (b), 5. (a)

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