R4RIN – MCQs, Mock Tests | NCERT Class 12 Current Electricity Class 12 MCQs Questions

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

✅ Correct Answer: 1

The resistance of a human body is about:

1. 2 Ω
2. 120 Ω
3. 12 KΩ
4. 120 MΩ

✅ Correct Answer: 3

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

✅ Correct Answer: 3

How many different resistances are possible with two equal resistors?

1. 2
2. 3
3. 4
4. 5

✅ Correct Answer: 2

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

1. 3
2. 4
3. 5
4. 6

✅ Correct Answer: 2

Specific resistance of ali metals is mostly affected by:

1. temperature
2. pressure
3. magnetic field
4. volume

✅ Correct Answer: 1

The example of a non-ohmic resistance is:

1. copper wire
2. fi lament lamp
3. carbon resistor
4. diode

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

✅ Correct Answer: 3

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

✅ Correct Answer: 1

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

1. halved (b) (c) (d)
2. doubled
3. unchanged
4. quadrupled

✅ Correct Answer: 1

In the above question, the conductance:

1. (a) halved
2. doubled
3. unchanged
4. quadrupled

✅ Correct Answer: 2

Siemen is the unit of:

1. resistance
2. conductance
3. specific conductance
4. None of the above

✅ Correct Answer: 2

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

✅ Correct Answer: 2

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

✅ Correct Answer: 3

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

✅ Correct Answer: 2

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

✅ Correct Answer: 3

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

✅ Correct Answer: 2

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

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

✅ Correct Answer: 2

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

1. very low
2. very high
3. varying
4. constant

✅ Correct Answer: 4

The emf of a car battery is about:

1. 2.5 V
2. 4.5 V
3. 8.6 V
4. 12 V

✅ Correct Answer: 4

Emf is measured in :

1. joule
2. joule/coulomb
3. joule-coulombs
4. joule/coulomb/metre

✅ Correct Answer: 2

1 kilowatt hour is commonly known as :

1. unit
2. 1 faraday
3. 1 curie
4. None of the above

✅ Correct Answer: 1

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

✅ Correct Answer: 3

The temperature coefficient of resistance is expressed in :

1. °C
2. °C-1
3. m°C-1
4. None of the above

✅ Correct Answer: 2

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

✅ Correct Answer: 2

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

✅ Correct Answer: 4

The phenomenon of super-conductivity was discovered by :

1. Ohm
2. Onnes
3. Edison
4. None of the above

✅ Correct Answer: 2

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

1. Tungsten
2. Carbon
3. Nichrome
4. Platinum

✅ Correct Answer: 2

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

✅ Correct Answer: 2

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

✅ Correct Answer: 4

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

✅ Correct Answer: 4

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 3

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

✅ Correct Answer: 3

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

1. R
2. 2 R
3. R/2
4. 6 R

✅ Correct Answer: 1

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

✅ Correct Answer: 2

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

✅ Correct Answer: 2

Thermo electricity was discovered by:

1. Joule
2. Peitier
3. Thomson
4. Seebeck

✅ Correct Answer: 4

Thermo emf is the order of:

1. 10 V
2. 10 V
3. 10 V
4. 10-12 V

✅ Correct Answer: 3