Current Electricity

A room heater is rated 400 W, 220 V. If the supply voltage drops to 200 V, what will be the power consumed (approximately) ?

1. 400 W
2. 121 W
3. 331 W
4. 200 W

A resistor is connected to a battery of 12 V emf and internal resistance 2 Ω. If the current in the circuit is 0.6 A, the terminal voltage of the battery is :

1. 12 V
2. 1.2 V
3. 10 V
4. 10.8 V

In a metre bridge experiment (see figure), the positions of the cell, E, and galvanometer, G, are interchanged. We shall observe in the galvanometer: [figure]

1. Only the right-sided deflection
2. Only the left-sided deflection
3. There will be no deflection irrespective of the position of the jockey
4. Both right-sided and left-sided deflection and at balance point, no deflection

A uniform metallic wire having resistance 4 Ω is bent to form a square loop (ABCD) (see figure). A resistance of 2 Ω is connected between points B and D and a battery of 2 V is connected across points A and C as shown in the figure. Now the value of current (I) is : [figure]

1. 4 A
2. 4.5 A
3. 8 A
4. 2 A

Consider two circuits, (A) and (B), each having two resistors. One of them has a positive temperature coefficient of resistance, + , while the other one has a negative temperature of coefficient, - , as shown in the figure. The current through these circuits are denoted by IA and IB. At initial temperature, the resistance of the two resistors is R0. As the temperature is increased, the correct option that describes the variation of current in these circuits is: [figure]

1. both IA and IB remain constant
2. IA remains constant while IB increases
3. IA decreases while IB increases
4. IA increases while IB decreases

The current passing through the battery in the given circuit, is: [figure]

1. 2.5 A
2. 1.5 A
3. 2.0 A
4. 0.5 A

A wire of resistance R is cut into 8 equal pieces. From these pieces two equivalent resistances are made by adding four of these together in parallel. Then these two sets are added in series. The net effective resistance of the combination is:

1. R16
2. R8
3. R64
4. R32

A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is: [figure]

1. 2.5 A
2. 3.0 A
3. 1.5 A
4. 2.0 A

The terminal voltage of the battery, whose emf is 10 V and internal resistance 1 , when connected through an external resistance of 4 as shown in the figure is: [figure]

1. 4 V
2. 6 V
3. 8 V
4. 10 V

A wire of length 'l' and resistance 100 is divided into 10 equal parts. The first 5 parts are connected in series while the next 5 parts are connected in parallel. The two combinations are again connected in series. The resistance of this final combination is:

1. 26
2. 52
3. 55
4. 60

Two heaters A and B have power rating of 1 kW and 2 kW, respectively. Those two are first connected in series and then in parallel to a fixed power source. The ratio of power outputs for these two cases is:

1. 1:1
2. 2:9
3. 1:2
4. 2:3

Choose the correct circuit which can achieve the bridge balance.

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

A uniform wire of diameter d carries a current of 100 mA when the mean drift velocity of electrons in the wire is v. For a wire of diameter d2 of the same material to carry a current of 200 mA, the mean drift velocity of electrons in the wire is

1. 4v
2. 8v
3. v
4. 2v

A uniform metal wire of length l has 10 resistance. Now this wire is stretched to a length 2l and then bent to form a perfect circle. The equivalent resistance across any arbitrary diameter of that circle is

1. 10
2. 5
3. 40
4. 20

The given circuit shows a uniform straight wire AB of 40 cm length fixed at both ends. In order to get zero reading in the galvanometer G, the free end of J is to be placed from B at: [figure]

1. 32 cm
2. 8 cm
3. 16 cm
4. 24 cm

The steady state current in the circuit shown below is : [figure]

1. 0.67 A
2. 1.5 A
3. 2 A
4. 1 A

The magnitude and direction of the current in the following circuit is :- [figure]

1. 0.5 A from A to B through E
2. 59 A from A to B through E
3. 1.5 A from B to A through E
4. 0.2 A from B to A through E

If the galvanometer G does not show any deflection in the circuit shown, the value of R is given by: [figure]

1. 50
2. 100
3. 400
4. 200

Resistance of a carbon resistor determined from colour codes is (22000 5\%) . The colour of third band must be :

1. Green
2. Orange
3. Yellow
4. Red

The resistance of platinum wire at 0 is 2 and 6.8 at 80 . The temperature coefficient of resistance of the wire is :

1. 3 10-3 -1
2. 3 10-2 -1
3. 3 10-10 -1
4. 3 10-4 -1

10 resistors, each of resistance R are connected in series to a battery of emf E and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased n times. The value of n is :

1. 100
2. 1
3. 1000
4. 10

As the temperature increases, the electrical resistance

1. Increases for both conductors and semiconductors
2. Decreases for both conductors and semiconductors
3. Increases for conductors but decreases for semiconductors
4. Decreases for conductors but increases for semiconductors

Two resistors of resistance, 100 and 200 are connected in parallel in an electrical circuit. The ratio of the thermal energy developed in 100 to that in 200 in a given time is

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

A copper wire of length 10 m and radius ( 10-2 ) m has electrical resistance of 10 . The current density in the wire for an electric field strength of 10 (V/m) is

1. 104 A/m2
2. 106 A/m2
3. 10-5 A/m2
4. 105 A/m2

A wheatstone bridge is used to determine the value of unknown resistance X by adjusting the variable resistance Y as shown in the figure. For the most precise measurement of X, the resistance P and Q [figure]

1. Should be approximately equal to 2X
2. Should be approximately equal and are small
3. Should be very large and unequal
4. Do not play any significant role

The reciprocal of resistance is :

1. conductance
2. reactance
3. mobility
4. conductivity

A cell of emf 4 V and internal resistance 0.5 is connected to a 7.5 external resistance. The terminal potential difference of the cell is

1. 0.375 V
2. 3.75 V
3. 4.25 V
4. 4 V

The equivalent resistance of the infinite network given below is : [figure]

1. (1 + 5 )
2. 2
3. (1 + 2 )
4. (1 + 3 )

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