Electricity and Magnetism MCQ question and answer with solution

71

Electricity and Magnetism mcq question image

Use of signal in an electrical circuit. It is indicated by . . . . . . . .?

A) Rheostat B) Resistor C) Wire joint D) Electric cell

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Answer & Solution

Answer: Option A

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72

Why does the core of a transformer is laminated?

A) To increase the electrical conductivity of the core B) To increase the magnetization of the core C) To reduce the eddy current loss D) To increase current and improve efficiency

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Answer & Solution

Answer: Option C

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73

What do the given symbol in figure represents in a reference of electric circuit?
Electricity and Magnetism mcq question image

A) resistance B) plug key C) electric bulb D) battery

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Answer & Solution

Answer: Option C

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74

An electric bulb of 100 W is used for 8 hours per day. The energy used by a bulb in a day is . . . . . . . . unit

A) 80 B) 800 C) 8 D) 0.8

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Answer & Solution

Answer: Option D

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75

To prevent damage from lightning, lightning conductors are used on tall structures. The lightning conductor

A) should be made of a good conductor, like copper with sharp pointed edges B) should be made of a good conductor but can be of any shape C) should be in the form of a vertical rod D) can be of any shape

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Answer & Solution

Answer: Option B

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76

The power of an electric bulb with 240 V and 0.6 A current will be . . . . . . . .?

A) 144 W B) 400 W C) 14.4 W D) 40 W

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Answer & Solution

Answer: Option A

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77

The purpose of choke in a fluorescent lamp is

A) to increase the current flow B) to decrease the current flow C) to decrease the resistance D) to decrease the voltage momentarily

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Answer & Solution

Answer: Option B

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78

What is electromagnetic induction?

A) The generation of electric current due to the relative motion between the coil and the magnetic field B) Generation of electrostatic force due to relative motion between the coil and the magnetic field C) Generation of electric current due to static current between the coil and the magnetic field D) The generation of electric current due to the relative motion between the induction motor and the magnetic field

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Answer & Solution

Answer: Option A

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79

The electromagnet has?

A) Soft iron core B) Steel core C) Nickel core D) Copper core

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Answer & Solution

Answer: Option A

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80

If the resistance of a conductor is reduced to half, its thermal effect will be . . . . . . . .

A) one fourth B) half C) double D) four times

Discuss

Answer & Solution

Answer: Option C

Solution:

The thermal effect of current refers to the heat produced in a conductor when an electric current flows through it, and it is given by Joule’s Law of Heating.

According to Joule’s Law, the heat produced (H) in a conductor is given by the formula:

H = I² R t

where I = current, R = resistance, and t = time.

If the resistance of the conductor is reduced to half, and the potential difference (V) remains constant, the current changes according to Ohm’s law:

I = V / R

When R is halved, the current becomes double (I' = 2I).

Now, substituting in the heat equation:

H' = I'² × R' × t = (2I)² × (R/2) × t = 4I² × (R/2) × t = 2I²Rt

This means that the new heat produced is double the original heat.

Therefore, when the resistance of a conductor is reduced to half (keeping voltage constant), its thermal effect doubles.

Hence, the correct answer is Option C: double.

Electricity and Magnetism MCQ question and answer with solution | Physics Gk MCQs