﻿ Engineering Entrance Exam Question and Answers | Current Electricity - Zigya

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Current Electricity

Multiple Choice Questions

1.

The Kirchhoff’s first law (∑ i= 0)   and second law (∑iR = ∑E), where the symbols have their usual meanings, are respectively based on

• conservation of charge, conservation of energy

• conservation of charge, conservation of momentum

• conservation of energy, conservation of charge

• conservation of energy, conservation of charge

A.

conservation of charge, conservation of energy

Kirchhoff's  Ist law or KCl states that the algebraic sum of current meeting at any junction is equal to zero. Thus, no charge has been accumulated at any junction i.e., the charge is conserved, and hence KCl is based on conservation of charge.

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2.

An energy source will supply a constant current into the load of its internal resistance is

• equal to the resistance of the load.

• very large as compared to the load resistance.

• zero

• zero

B.

very large as compared to the load resistance.

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3.

A material ‘B’ has twice the specific resistance of ‘A’. A circular wire made of ‘B’ has twice the diameter of a wire made of ‘A’. Then for the two wires to have the same resistance, the ratio

• 2

• 1

• 1/4

• 1/4

A.

2

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4.

The resistance of the series combination of two resistances is S. When they are joined in parallel through total resistance is P. If S = nP, then the minimum possible value of n is

• 4

• 3

• 2

• 2

A.

4

Let the resistance R1 and R2

So, S = R1+ R2;

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5.

An electric current is passed through a circuit containing two wires of the same material, connected in parallel. If the length and radii of the wires are in the ratio of 4/3 and 2/3, then the ratio of the currents passing through the wire will be

• 3

• 1/3

• 8/9

• 8/9

B.

1/3

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6.

Two thin, long parallel wires separated by a distance  ‘d’ carry a current of ‘i’ A in the same direction. They will

• attract each other with a force of µ0i2/(2πd)

• repel each other with a force of µ0i2/(2πd)

• attract each other with a force of µ0i2(2πd2 )

• attract each other with a force of µ0i2(2πd2 )

A.

attract each other with a force of µ0i2/(2πd)

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7.

In a metre bridge experiment null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y. If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4X against Y?

• 50 cm

• 80 cm

• 40 cm

• 40 cm

A.

50 cm

We have from meter bridge experiment,

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8.

The total current supplied to the circuit by the battery is

• 1A

• 2 A

• 4 A

• 4 A

C.

4 A

The given circle is written as
I = V/R
I = 6 V / 1.5 Ω
= 4 A

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9.

In a Wheatstone’s bridge, there resistances P, Q and R connected in the three arms and the fourth arm is formed by two resistances S1 and S2 connected in parallel. The condition for bridge to be balanced will be

A.

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10.

The electrochemical equivalent of a metal is 3.3 × 10−7 kg per coulomb. The mass of the metal liberated at the cathode when a 3 A current is passed for 2 seconds will be

• 19.8 × 10−7 kg

• 9.9 × 10−7 kg

• 6.6 × 10−7 kg

• 6.6 × 10−7 kg

A.

19.8 × 10−7 kg

Mass of substance liberated at cathode m = zit
where, z = electro-chemical equivalent = 3.3× 10-7 kg/C
i = current flowing = 3A.
t = 2 sec
∴ m = 3.3× 10-7× 3× 2
= 19.8× 10-7 kg

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