#### The AC voltage across a resistance can be measured using a : Option 1)  potentiometer   Option 2) moving coil galvanometer Option 3) moving magnet galvanometer   Option 4) hot wire voltmeter

As we learnt in

To determine the resistance of a galvanometer by half deflection method -

G= galvanometre resistance

R= Extreme resistance

S= Shunt

Procedure

Resistance of galvanometer by half deflection method.

1.    Draw the circuit diagram as shown in figure.

2.    See that plugs of the resistance boxes are tight.

3.    Take out high resistance  from the resistance box R and insert the key K1 only.

4.    Adjust the value of R so that deflection is maximum, even in number and within scale.

5.    Note the deflection. Let it be .

6.    Now, insert the key K2 and without changing the value of R adjust the value of S such that deflection in the galvanometer reduces to exactly half the value obtained in step 5 i.e.

7.    Note the value of resistance S.

8.    Repeat steps 4 to 7 three times taking out different values of R and adjusting S every time.

- wherein

= definite angle

Ig  = current passing through galvanometre

K= figuring merit

Moving coil or magnet galvanometer can measure only d.c. values. For A.C. voltage hot wire voltmeter is used.

Option 1)

potentiometer

This option is incorrect

Option 2)

moving coil galvanometer

This option is incorrect

Option 3)

moving magnet galvanometer

This option is incorrect

Option 4)

hot wire voltmeter

This option is correct