Current Electricity · Question 28

The sliding contact C is at one fourth of the length of the potentiometer wire (AB) from A as shown in the circuit diagram. If the resistance of the wire AB is R0, then the potential drop (V) across the resistor R is [figure]

1. 2V0 R2R0 + 3R
2. 4V0 R3R0 + 16R
3. 4V0 R3R0 + R
4. 2V0 R4R0 + R

In a potentiometer circuit a cell of EMF 1.5 V gives balance point at 36 cm length of wire. If another cell of EMF 2.5 V replaces the first cell, then at what length of the wire, the balance point occurs?

1. 62 cm
2. 60 cm
3. 21.6 cm
4. 64 cm

The effective resistance of a parallel connection that consists of four wires of equal length, equal area of cross-section and same material is 0.25 . What will be the effective resistance if they are connected in series?

1. 4
2. 0.25
3. 0.5
4. 1

Column - I gives certain physical terms associated with flow of current through a metallic conductor. Column-II gives some mathematical relations involving electrical quantities. Match column-I and column-II with appropriate relations.

1. (A)-(R); (B)-(Q); (C)-(S); (D)-(P)
2. (A)-(R); (B)-(S); (C)-(P); (D)-(Q)
3. (A)-(R); (B)-(S); (C)-(Q); (D)-(P)
4. (A)-(R); (B)-(P); (C)-(S); (D)-(Q)

Three resistors having resistances r1, r2 and r3 are connected as shown in the given circuit. The ratio i3i1 of currents in terms of resistances used in the circuit is : [figure]

1. r2r1+r3
2. r1r2+r3
3. r2r2+r3
4. r1r1+r2

A resistance wire connected in the left gap of a metre bridge balances a 10 resistance in the right gap at a point which divides the bridge wire in the ratio 3:2. If the length of the resistance wire is 1.5 m, then the length of 1 of the resistance wire is :

1. 1.0 10-1 m
2. 1.5 10-1 m
3. 1.5 10-2 m
4. 1.0 10-2 m

The color code of a resistance is given below : [figure] The values of resistance and tolerance, respectively, are

1. 47 k , 10%
2. 4.7 k , 5%
3. 470 , 5%
4. 470 k , 5%

A charged particle having drift velocity 7.5 10-4 m s-1 in an electric field of 3 10-10 V m-1 has a mobility in m2 V-1 s-1 of :

1. 2.5 106
2. 2.5 10-6
3. 2.25 10-15
4. 2.25 1015

Which of the following graph represents the variation of resistivity ( ) with temperature (T) for copper?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

The solids which have the negative temperature coefficient of resistance are :

1. insulators only
2. semiconductors only
3. insulators and semiconductors
4. metals