For measurement of potential difference, the potentiometer is preferred in comparison to the voltmeter because:

1. the potentiometer is more sensitive than the voltmeter.

2. the resistance of the potentiometer is less than
    the voltmeter.

3. the potentiometer is cheaper than the voltmeter.

4. the potentiometer does not take current from the circuit.

In Wheatstone's bridge P = 9 ohm, Q = 11 ohm, R = 4 ohm and S = 6 ohm. How much resistance must be put in parallel to the resistance S to balance the bridge 

(1) 24 ohm

(2) $\frac{44}{9}$ohm

(3) 26.4 ohm

(4) 18.7 ohm

A potentiometer is an ideal device of measuring potential difference because

(1) It uses a sensitive galvanometer

(2) It does not disturb the potential difference it measures

(3) It is an elaborate arrangement

(4) It has a long wire hence heat developed is quickly radiated

A battery of 6 volts is connected to the terminals of a three metre long wire of uniform thickness and resistance of the order of 100 Ω. The difference of potential between two points separated by 50cm on the wire will be :

(1) 1 V

(2) 1.5 V

(3) 2 V

(4) 3 V

A potentiometer is used for the comparison of e.m.f. of two cells E₁ and E₂. For cell E₁ the no deflection point is obtained at 20cm and for E₂ the no deflection point is obtained at 30cm. The ratio of their e.m.f.'s will be 

(1) 2/3

(2) 1/2

(3) 1

(4) 2

If the length of the potentiometer wire is increased, then the length of the previously obtained balance point will :

(1) Increase

(2) Decrease

(3) Remain unchanged

(4) Become two times

If in the experiment of Wheatstone's bridge, the positions of cells and galvanometer are interchanged, then balance points will

(1) Change

(2) Remain unchanged

(3) Depend on the internal resistance of cell and resistance of galvanometer

(4) None of these

Two cells when connected in series are balanced on 8m on a potentiometer. If the cells are connected with polarities of one of the cells  reversed, they balance on 2m. The ratio of e.m.f.'s of the two cells is

(1) 3 : 5

(2) 5 : 3

(3) 3 : 4

(4) 4 : 3

In the diagram shown, the reading of voltmeter is 20 V and that of ammeter is 4 A. The value of R should be (consider given ammeter and voltmeter are not ideal) :

(1) Equal to 5 Ω

(2) Greater from 5 Ω

(3) Less than 5 Ω

(4) Greater or less than 5 Ω depends on the material of R