Current Electricity

A Wheatstone bridge is initially at room temperature and all arms of the bridge have same value of resistances (R1 = R2 = R3 = R4). When R3 resistance is heated to some temperature, its resistance value has gone up by 10%. The potential difference (Va - Vb) (after R3 is heated) is V. [figure]

1. 1.05
2. 0.95
3. 0
4. 2

Two resistors 2 and 3 are connected in the gaps of bridge as shown in figure. The null point is obtained with the contact of jockey at some point on wire XY. When an unknown resistor is connected in parallel with 3 resistor, the null point is shifted by 22.5 cm toward Y. The resistance of unknown resistor is . [figure]

1. 3
2. 1
3. 4
4. 2

In a meter bridge experiment to determine the value of unknown resistance, first the resistances 2 and 3 are connected in the left and right gaps of the bridge and the null point is obtained at a distance l cm from the left. Now when an unknown resistance x is connected in parallel to 3 resistance, the null point is shifted by 10 cm to the right of wire. The value of unknown resistance x is .

A meter bridge with two resistances R1 and R2 as shown in figure was balanced (null point) at 40 cm from the point P. The null point changed to 50 cm from the point P, when 16 resistance is connected in parallel to R2. The values of resistances R1 and R2 are . [figure]

1. R2 = 8 , R1 = 163
2. R2 = 12 , R1 = 123
3. R2 = 4 , R1 = 43
4. R2 = 16 , R1 = 163

The heat generated in 1 minute between points A and B in the given circuit, when a battery of 9 V with internal resistance of 1 is connected across these points is J. [figure]

The total length of potentiometer wire AB is 50 cm in the arrangement as shown in the figure. If P is the point where the galvanometer shows zero reading then the length AP is cm. [figure]

1. 25
2. 30
3. 15
4. 20

The value of current I in the electrical circuit as given below, when potential at A is equal to the potential at B, will be A. [figure]