Current Electricity

The ratio of heat dissipated per second through the resistance 5 and 10 in the circuit given below is: [figure]

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

A wire of resistance 20 is divided into 10 equal parts. A combination of two parts are connected in parallel and so on. Now resulting pairs of parallel combination are connected in series. The equivalent resistance of final combination is .

The resistances of the platinum wire of a platinum resistance thermometer at the ice point and steam point are 8 and 10 respectively. After inserting in a hot bath of temperature 400 , the resistance of platinum wire is :

1. 10
2. 16
3. 8
4. 2

To measure the internal resistance of a battery, potentiometer is used. For R=10 , the balance point is observed at l=500 cm and for R=1 the balance point is observed at l=400 cm. The internal resistance of the battery is approximately :

1. 0.1
2. 0.3
3. 0.2
4. 0.4

Twelve wires each having resistance 2 are joined to form a cube. A battery of 6 V emf is joined across points a and c. The voltage difference between e and f is V. [figure]

An electric bulb rated 50 W–200 V is connected across a 100 V supply. The power dissipation of the bulb is:

1. 100 W
2. 50 W
3. 12.5 W
4. 25 W

Two wires A and B are made up of the same material and have the same mass. Wire A has radius of 2.0 mm and wire B has radius of 4.0 mm. The resistance of wire B is 2 . The resistance of wire A is .

The reading in the ideal voltmeter (V) shown in the given circuit diagram is : [figure]

1. 3 V
2. 10 V
3. 5 V
4. 0 V

The current in a conductor is expressed as I = 3t2 + 4t3, where I is in Ampere and t is in second. The amount of electric charge that flows through a section of the conductor during t = 1 s to t = 2 s is C.

In a metre-bridge when a resistance in the left gap is 2 and unknown resistance in the right gap, the balance length is found to be 40 cm. On shunting the unknown resistance with 2 , the balance length changes by :

1. 62.5 cm
2. 22.5 cm
3. 20 cm
4. 65 cm

To measure the temperature coefficient of resistivity of a semiconductor, an electrical arrangement shown in the figure is prepared. The arm BC is made up of the semiconductor. The experiment is being conducted at 25 and resistance of the semiconductor arm is 3 m . Arm BC is cooled at a constant rate of 2 /s. If the galvanometer G shows no deflection after 10 s, then is : [figure]

1. -1 10-2 C-1
2. -2 10-2 C-1
3. -2.5 10-2 C-1
4. -1.5 10-2 C-1

In an electrical circuit drawn below the amount of charge stored in the capacitor is . [figure]

Two conductors have the same resistances at 0 C but their temperature coefficients of resistance are 1 and 2. The respective temperature coefficients for their series and parallel combinations are :

1. 1+ 2, 1 2 1+ 2
2. 1+ 22, 1+ 22
3. 1+ 2, 1+ 22
4. 1+ 22, 1+ 2

Equivalent resistance of the following network is . [figure]

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

1. 26%
2. 36%
3. 46%
4. 56%

The resistance per centimeter of a meter bridge wire is r, with X resistance in left gap. Balancing length from left end is at 40 cm with 25 resistance in right gap. Now the wire is replaced by another wire of 2r resistance per centimeter. The new balancing length for same settings will be at

1. 10 cm
2. 80 cm
3. 40 cm
4. 20 cm

In the following circuit, the battery has an emf of 2 V and an internal resistance of 23 . The power consumption in the entire circuit is W. [figure]

A potential divider circuit is shown in figure. The output voltage V0 is : [figure]

1. 2 mV
2. 4 V
3. 0.5 V
4. 12 mV

An electric toaster has resistance of 60 at room temperature (27 ). The toaster is connected to a 220 V supply. If the current flowing through it reaches 2.75 A, the temperature attained by toaster is around : ( if =2 10-4/ )

1. 1235
2. 1667
3. 694
4. 1694

Two cells are connected in opposition as shown. Cell E1 is of 8 V emf and 2 internal resistance; the cell E2 is of 2 V emf and 4 internal resistance. The terminal potential difference of cell E2 is V. [figure]

When a potential difference V is applied across a wire of resistance R, it dissipates energy at a rate W. If the wire is cut into two halves and these halves are connected mutually parallel across the same supply, the energy dissipation rate will become:

1. 1/2W
2. 4W
3. 1/4W
4. 2W

Two resistances of 100 and 200 are connected in series with a battery of 4 V and negligible internal resistance. A voltmeter is used to measure voltage across 100 resistance, which gives reading as 1 V. The resistance of voltmeter must be .

The electric current through a wire varies with time as I=I0+ t, where I0=20 A and =3 A/s. The amount of electric charge crossed through a section of the wire in 20 s is :

1. 80 C
2. 800 C
3. 1000 C
4. 1600 C

In the given circuit, the current in resistance R3 is : [figure]

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

In the given circuit, the current flowing through the resistance 20 is 0.3 A, while the ammeter reads 0.9 A. The value of R1 is . [figure]

In the given figure, the charge stored in 6 capacitor, when points A and B are joined by a connecting wire is . [figure]

A wire of length 10 cm and radius 7 10-4 m is connected across the right gap of a meter bridge. When a resistance of 4.5 is connected on the left gap by using a resistance box, the balance length is found to be at 60 cm from the left end. If the resistivity of the wire is R 10-7 , then value of R is :

1. 63
2. 70
3. 66
4. 35

A wire of resistance R and length L is cut into 5 equal parts. If these parts are joined parallely, then resultant resistance will be :

1. 125R
2. 15R
3. 25 R
4. 5 R

Three voltmeters, all having different internal resistances are joined as shown in figure. When some potential difference is applied across A and B, their readings are V1, V2 and V3. Choose the correct option. [figure]

1. V1=V2
2. V1 V3-V2
3. V1+V2=V3
4. V1+V2>V3

Wheatstone bridge principle is used to measure the specific resistance (S1) of given wire, having length L, radius r. If X is the resistance of wire, then specific resistance is ; S1=X ( r2L ). If the length of the wire gets doubled then the value of specific resistance will be :

1. S14
2. 2 S1
3. S12
4. S1