Electricity Test

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Electricity Test - 16

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following is/are good conductor(s) of electricity?

A
Metals, Mica

B
Metals, Rubber

C
Mica, Quartz

D
Metals, Quartz

Solution

Metals are electropositive in nature and are therefore, good conductors of electricity. Quartz is a chemical compound consisting of one part silicon and two parts oxygen $(S i O_{2})$ . It is the most abundant mineral found in Earth's surface. Its unique properties make it one of the most useful natural substances. It has electrical properties and heat resistance that make it valuable in electronic products. Mica has superior electrical properties as an insulator. Rubber is also an insulator.
Hence, the correct option is (D).
Question 2
1 / -0

$0.5$ coulombs of charge flows through a conductor in $2$ seconds. What is the magnitude of the current flowing through the conductor?

A
$0.25 A$

B
$0.5 A$

C
$0.2 A$

D
$1 A$

Solution

Electrical current is a measure of the amount of electrical charge transferred per unit of time. It represents the flow of electrons through a conductive material, such as a metal wire. It is measured in amperes.
Given charge $Q = 0.5 C$
Time $t = 2 s e c$
Let the magnitude of the current flowing through the conductor be $I$ .
Therefore, $I = \frac{Q}{t}$
$= \frac{0.5}{2}$
$= 0.25 A$
Hence, the correct option is (A).
Question 3
1 / -0

When a steady current flows through a conductor, the electrons in it move with certain average speed known as:

A
Drift speed

B
Accelerated speed

C
Root mean square speed

D
Average velocity

Solution

The drift velocity is the average velocity that a particle, such as electrons, attains in a material due to a steady electric field. It can also be referred to as axial drift velocity.
Hence, the correct option is (A).
Question 4
1 / -0

Calculate the resistance of a conductor if the current flowing through it is $0.2 A$ , when potential difference applied is $0.8 V$ .

A
$0.25 Ω$

B
$4 Ω$

C
$3 Ω$

D
$5 Ω$

Solution

Given, potential difference across the conductor, $V = 0.8 V$ ; current flowing through the conductor $= 0.2 A$
According to Ohm's law, the resistance of the conductor is given by: $R = \frac{V}{I}$
Therefore, $R = \frac{0.8 V}{0.2 A}$
or $R = 4 Ω$
Hence, the correct option is (B).
Question 5
1 / -0

Find the incorrect statement:

A
The SI unit of electric charge is coulomb.

B
The P. D. for all the resistors in the parallel circuit remains constan

C
The direction of flow of negative charge was taken to be the direction of electric current.

D
None of these

Solution

As a convention, the direction of flow of positive charge was taken to be the direction of electric current. The direction of flow of electrons is opposite to the direction of conventional current.
Hence, the correct option is (C).
Question 6
1 / -0

Which of the following is incorrect about the heat produced in a resistor?

A
Directly proportional to the time for which the current flows through the resistors.

B
Directly proportional to the resistance for a given current

C
It is directly proportional to the square of the current.

D
None of these

Solution

According to Joule's law of heating, the heat produced in a resistor is directly proportional to the square of the current for a given resistance, directly proportional to the resistance for a given current and directly proportional to the time for which the current flows through the resistor.
$H = I^{2} R t$
Hence, the correct option is (D).
Question 7
1 / -0

The number of electrons present in one coulomb of charge is:

A
$6 \times 10^{- 19}$

B
$6 \times 10^{19}$

C
$6 \times 10^{18}$

D
$6 \times 10^{20}$

Solution

$Q = n \times e$
Therefore, the number of electrons present in one coulomb of charge,
$n = \frac{1}{1.6 \times 10^{- 19}}$
or $n = \frac{10 \times 10^{18}}{1.6}$
Hence, the correct option is (C).
Question 8
1 / -0

In an electric circuit, the direction of electric current is:

A
from the positive terminal to the positive terminal.

B
from the positive terminal to the negative terminal.

C
from the negative terminal to the negative terminal.

D
from the negative terminal to the positive terminal.

Solution

In an electric circuit, the direction of electric current is from the positive terminal of the battery to the negative terminal of the battery. This is as per convention. Electrons were not known at the time when the phenomenon of electricity was first discovered. Electric current was considered to be the flow of positive charges and the direction of flow of positive charges was taken to be the direction of electric current.
Hence, the correct option is (B).
Question 9
1 / -0

Which of the following fuse should be used for an electric iron of $1 k W$ when operated at $220 V$ ?

A
$1 A$

B
$7 A$

C
$5 A$

D
$3 A$

Solution

Current rating of the fuse,
$I > \frac{P}{V}$
or $I > \frac{1000}{220}$
or $I > 4.55 A$ .
A fuse is a device used in electrical systems to protect against excessive current, the appropriate fuse for the electric iron at $220 V$ would be that of $5 A$ .
Hence, the correct option is (C).
Question 10
1 / -0

Why is tungsten used exclusively for the filament of an incandescent lamp?

A
The melting point of tungsten is very high.

B
Tungsten has a fairly good resistivity.

C
Tungsten can be drawn into thin wires which in turn offers high resistance.

D
All of these

Solution

Tungsten $(W)$ is exclusively used for making filaments of electric bulbs. Tungsten has a fairly good resistivity $(5.20 \times 10^{- 8} Ω m)$ at $20^{\circ} C$ . Tungsten is ductile and can be drawn into thin wires. Thin wires offer high resistance, offer great heating effect and produces light $(H = I^{2} R t)$ . The thin wires of tungsten do not melt at high temperatures since the melting point of tungsten is very high ( $3380^{\circ} C$ ).
Hence, the correct option is (D).
Question 11
1 / -0

How is an ammeter connected in an electric circuit?

A
Sometimes in series and sometimes in parallel

B
In parallel

C
In series

D
None of these

Solution

An ammeter is always connected in series in an electric circuit. It is likely to burn out if connected in parallel.
Hence, the correct option is (C).
Question 12
1 / -0

The function of rheostat in an electrical circuit is to:

A
Change the resistance in the circuit

B
Increase the resistance in the circuit

C
Decrease the resistance in the circuit

D
None of these

Solution

A Rheostat is an electrical instrument used to control current in a circuit by varying the resistance. The resistance can be decreased or increased with the help of a rheostat.
Hence, the correct option is (A).
Question 13
1 / -0

‘Electrons are consumed in an electric circuit’.
The above statement is:

A
Partially true

B
True

C
False

D
Partially false

Solution

Electrons are not consumed in an electrical circuit. The energy provided to an electric circuit moves electrons through gadgets like electric iron, bulbs, etc.
Hence, the correct option is (C).
Question 14
1 / -0

The melting point of Tungsten is:

A
$3422^{\circ} C$

B
$4000^{\circ} C$

C
$3500^{\circ} C$

D
$3333^{\circ} C$

Solution

Tungsten is remarkable for its robustness, especially the fact that it has the highest melting point of all the elements discovered. It has a melting point of $3422^{\circ} C$ .
Hence, the correct option is (A).
Question 15
1 / -0

Nichrome wire is commonly used in heating elements because of its_______.

A
Low specific resistance

B
Low melting point

C
High specific resistance

D
High conductivity

Solution

Due to the high specific resistance of Nichrome, the resistance of a nichrome wire of a finite length is high. Hence when a particular amount of current is passed through the wire, the power of heating, I²R, has a large value and hence it heats more quickly as compared to other materials.
Hence, the correct option is (C).

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Electricity Test - 16

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Electricity Test - 16

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Question 1

Metals, Mica

Metals, Rubber

Mica, Quartz

Metals, Quartz

Solution

Question 2

0.25 A

0.5 A

0.2 A

1 A

Solution

Question 3

Drift speed

Accelerated speed

Root mean square speed

Average velocity

Solution

Question 4

0.25 Ω

4 Ω

3 Ω

5Ω

Solution

Question 5

The SI unit of electric charge is coulomb.

The P. D. for all the resistors in the parallel circuit remains constan

The direction of flow of negative charge was taken to be the direction of electric current.

None of these

Solution

Question 6

Directly proportional to the time for which the current flows through the resistors.

Directly proportional to the resistance for a given current

It is directly proportional to the square of the current.

None of these

Solution

Question 7

6×10−19

6×1019

6×1018

6×1020

Solution

Question 8

from the positive terminal to the positive terminal.

from the positive terminal to the negative terminal.

from the negative terminal to the negative terminal.

from the negative terminal to the positive terminal.

Solution

Question 9

1 A

7 A

5 A

3 A

Solution

Question 10

The melting point of tungsten is very high.

Tungsten has a fairly good resistivity.

Tungsten can be drawn into thin wires which in turn offers high resistance.

All of these

Solution

Question 11

Sometimes in series and sometimes in parallel

In parallel

In series

None of these

Solution

Question 12

Change the resistance in the circuit

Increase the resistance in the circuit

Decrease the resistance in the circuit

None of these

Solution

$0.25 A$

$0.5 A$

$0.2 A$

$1 A$

$0.25 Ω$

$4 Ω$

$3 Ω$

$5 Ω$

$6 \times 10^{- 19}$

$6 \times 10^{19}$

$6 \times 10^{18}$

$6 \times 10^{20}$

$1 A$

$7 A$

$5 A$

$3 A$

$3422^{\circ} C$

$4000^{\circ} C$

$3500^{\circ} C$

$3333^{\circ} C$