NCERT Class 12/Current Electricity Class 12 MCQs Questions Sample Test,Sample questions

Question:
1 kilowatt hour is commonly known as :

1.unit

2.1 faraday

3.1 curie

4.None of the above


Question:
A 5 A fuse wire can with stand a maximum power of 1 W in circuit. The resistance of the fuse wire is:

1.0.2 Ω

2.5 Ω

3.0.4 Ω

4.0.04 Ω


Question:
A galvanometer acting as a volt meter will have with its coil.

1.a high resistance in parallel

2.a high resistance in series

3.a low resistance in parallel

4.a low resistance in series


Question:
A potential difference of 10 V is applied across a conductance of 2 S. The current in the conductor will be :

1.20 A

2.5 A

3.0.2 A

4.None of the above


Question:
A potential difference of 10 V is applied across a conductance of 2 S. The current in the conductor will be :

1.20 A

2.5 A

3.0.2 A

4.None of the above


Question:
A potential difference of 10 V is applied across a conductance of 2 S. The current in the conductor will be :

1.20 A

2.5 A

3.0.2 A

4.None of the above


Question:
A uniform w ire connected across a supply produces heat H per second. If wire is cut into three equal parts and all the parts are connected in parallel across the same supply, the heat produced per second will

1.H/9

2.9 H

3.3 H

4.H/3


Question:
A wire of resistance 3 Ω is cut into three pieces, which are then joined to form a triangle. The equivalent resistance between any corners of the triangle is :

1.2/3 Ω

2.3/2 Ω

3.1/2 Ω

4.1/3 Ω


Question:
A wire P is half the diameter and half the length of a wire Q of similar material. The ratio of resistances of P to that 0 is:

1.4 : 1

2.8 : 1

3.2 : 1

4.1 : 2


Question:
An electric heating element consumes 500 W, when connected to a 100 V line. If the line voltage becomes 150 V, the power consumed Will be:

1.500 W

2.730 W

3.1000 W

4.1125 W


Question:
Copper wire is used as connecting wire because :

1.copper has high electrical resistivity

2.copper has low electrical resistivity

3.copper has low electrical conductivity

4.copper has high value of elasticity


Question:
Emf is measured in :

1.joule

2.joule/coulomb

3.joule-coulombs

4.joule/coulomb/metre


Question:
Given three equal resistors, how many different combinations (taken all of them together) can be made?

1.3

2.4

3.5

4.6


Question:
How many different resistances are possible with two equal resistors?

1.2

2.3

3.4

4.5


Question:
How many joules are equal to I kWh ?

1.3.6 × 104

2.3.6 × 105

3.3.6 × 106

4.None of the above


Question:
How much electric energy is consumed by a 100 W lamp used for 6 hours everyday for 30 days?

1.18 kJ

2.18 kWh

3.1.8 J

4.None of the above


Question:
If a certain piece of copper is to be shaped into a conductor of minimum resistance, its length (L) and cross-sectional area (a) shall respectively be :

1. L, 2A

2.L/2, 2A

3.2L, 2A

4.2l, A/2


Question:
In a Wheatstone bridge, the resistance each arm is 10 Ω. If the resistance galvanometers is also 10 Ω, then effective resistance of the bridge will be :

1.40 Ω

2.20 Ω

3.10 Ω

4.5 Ω


Question:
In questions 135, w hen the wires are connected in series, the heat produced in the thinner wire is H1 and that in the thicker wire is H2. Then :

1.H1 = H2

2.H1 < H2

3.H1 > H2

4.H1 > H2


Question:
In the above question, the conductance:

1.(a) halved

2.doubled

3.unchanged

4.quadrupled


Question:
Kirchhoffs first and second laws for electrical circuits are consequences of:

1.conservation of energy

2.conservation of electrical charge and energy respectively

3.conservation of electric charge

4.neither conservation of energy nor electric charge


Question:
n an experiment with potentiometer, null point with a cell is found at 240 cm. When the cell is shunted with a resistance 2 Ω, the null point becomes 120 cm internal resistance of cell is :

1.4 Ω

2.2 Ω

3.1Ω

4.1/2 Ω


Question:
n India electricity is supplied fordomestic use at 220 V. It is supplied at 110 V in U.S.A. If the resistance of a 60 W bulb use in India is R. the resistance of a 60 W bulb for use in USA will be:

1.2 R

2.R

3. R/2

4.R/4


Question:
n resistances, each of R Ω, are connected in parallel gives an equivalent resistance of R Ω. If these resistances were , connected in series, the combination would have a resistance in Ω is equal to

1. n²R

2.R/n²

3.R/n

4. nR


Question:
Ohm’s law is valid when the temperature of conductor is :

1.very low

2. very high

3.varying

4. constant


Question:
Potentiometer measures the potential difference more accurately than a voltmeter because:

1. It has a wire of high resistance

2.It has a wire of low resistance

3.It does not draw current from external circuit

4. It draws heavy current from external circuit


Question:
Siemen is the unit of:

1.resistance

2.conductance

3.specific conductance

4.None of the above


Question:
Specific resistance of ali metals is mostly affected by:

1.temperature

2.pressure

3.magnetic field

4.volume


Question:
Suppose H1 is the heat generated per second in the filament of a 100 W, 250 V lamp and H2 is the heat generated in the filament of a 200 W, 250 V lamp. Then H1/H2 is equal to:

1.1

2.2

3.1/2

4.1/4


Question:
The emf of a car battery is about:

1.2.5 V

2.4.5 V

3.8.6 V

4.12 V


Question:
The example of a non-ohmic resistance is:

1.copper wire

2.fi lament lamp

3.carbon resistor

4.diode


Question:
The heat sensitive device whose resistivity changes very rapidly with change of temperature is called a :

1.resistor

2.super-conductor

3.thermocouple

4.thermistor


Question:
The length and radius of an electric resistance of a certain wire are doubled simultaneously, then the:

1.resistance will be doubled and specific resistance will be halved

2.resistance will be halved and specific resistance will remain uncharged

3.resistance will be halved and the specific resistance will be doubled

4.resistance and specific resistance will both remain uncharged


Question:
The length of a conductor is halved. Its resistance will be :

1.halved (b) (c) (d)

2.doubled

3.unchanged

4.quadrupled


Question:
The number of electrons that constitute 1 A of current is:

1.6.25 × 1016

2.6.25 × 1017

3.6.25 × 1018

4.6.25 × 1019


Question:
The phenomenon of super-conductivity was discovered by :

1.Ohm

2.Onnes

3.Edison

4.None of the above


Question:
The resistance of a human body is about:

1.2 Ω

2.120 Ω

3.12 KΩ

4.120 MΩ


Question:
The specific resistance of a conductor increases with :

1.increase in temperature

2.increase in cross-sectional area

3.decrease in length

4.decrease in cross-sectional area


Question:
The specific resistance of a rod of copper as compared to that of thin wire of copper is :

1. less

2.more

3.same

4.depends upon the length and area of cross-section of the wire


Question:
The speed at which tjie current travels in a conductor is nearly:

1.3 × 104 ms-1

2.3 × 106 ms-1

3.3 × 108 ms-1

4.3 × 1010 ms-1


Question:
The temperature coefficient of resistance is expressed in :

1.°C

2.°C-1

3.m°C-1

4.None of the above


Question:
Thermo electricity was discovered by:

1.Joule

2.Peitier

3.Thomson

4.Seebeck


Question:
Thermo emf is the order of:

1.10 V

2.10 V

3.10 V

4.10-12 V


Question:
Two bulbs 25 W, 220 V and 100 W, 220 V are given. Which has higher resistance?

1.25 W

2.100 W

3.both bulbs have equal resistance

4.resistance of bulbs can not be compared


Question:
Two equal resistors are connected in series across a battery and consume a power of P. If these are connected in parallel, then the’ power consumed will be:

1.2P

2.4 P

3.p/4

4.P


Question:
Two wires of copper are of the same length but’have different diameters. When they are connected in series across a battery, the heat generated is H1 When connected in parallel across the same battery, the heat generated during the same time is H2 Then :

1.H1 = H2

2.H1 < H2

3.H1 > H2

4.H1 > H2


Question:
What is the resistance across A and B in the network in Fig.?

1. R

2.2 R

3.R/2

4.6 R


Question:
When the wires are connected in parallel, the heat produced in the thinner wire is H1 and that in the thicker wire is H2 Then:

1. H1 = H2

2.H1 < H2

3.H1 > H2

4. H1 ≥ H2


Question:
When three identical bulbs of 60 W, 200 V rating are connected in series to a 200 V supply, the power drawn by them will be:

1.20 W

2.60 W

3.180 W

4.10 W


Question:
Which of the following has a negative temperature coefficient of resistance ?

1.Tungsten

2.Carbon

3.Nichrome

4.Platinum


Question:
Why is the Wheatstone bridge more accurate than other methods of measuring resistances: ‘

1.It is a null method

2. It is based on Kirchhoffs laws

3.It has four resistances

4.It does not involve ohm’s law


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