Electricity(10th Grade > Physics ) Questions and answers for exam Preparation

10th Grade > Physics

ELECTRICITY MCQs

Total Questions : 244 | Page 3 of 25 pages

Question 21. Two resistances of 100 Ω and 0 Ω are connected in parallel. The overall resistance will be:

100 Ω
50 Ω
25 Ω
0 Ω

Discuss Question

Answer: Option D. -> 0 Ω
:
D
Effective Resistance

(R_{e})

when 2 resistors, let (

R_{1} a n d R_{2}

)are in parallel is given by

(R_{e})

\frac{R_{1} \times R_{2}}{R_{1} + R_{2}}

Given :

R_{1} = 100 Ω

R_{2} = 0 Ω

(R_{e}) = \frac{100 \times 0}{100 + 0} = 0

Question 22. When the current in a conductor is doubled, keeping its resistance constant, the heat generated in the conductor will be:

double of the original
4 times of the original
3 times of the original
8 times of the original

Discuss Question

Answer: Option B. -> 4 times of the original
:
B
We know heat produced in a conductor is

H = I^{2} R t

, where '

I

' is the current flowing, '

R

' is the resistance of wire and '

t

' is the time for which current is flowing in a conductor.
When electrical resistance '

R

' and time period '

t

' is kept constant then,

H \propto I^{2}

.
So, if the current is doubled, the heating effect of a current through a conductor becomes 4 times of the original.

Question 23. Three resistances each of 4 Ohm are connected in the form of an equilateral triangle. The effective resistance between any two corners is:

38 Ohm
83 Ohm
8 Ohm
12 Ohm

Discuss Question

Answer: Option B. -> 83 Ohm
:
B
Two in series = 8 Ohm
This 8 Ohm will be parallel to 4 Ohm which gives a resultant =(

\frac{4 \times 8}{4 + 8}) = (\frac{8}{3}) O h m

Question 24.

The device which measures the electric potential difference between two points is called as ___.

ammeter
voltmeter
potentiometer
ohmmeter

Discuss Question

Answer: Option B. -> voltmeter
:
B
The device which measures the electric potential difference between two points is known as a voltmeter. It is attached in parallel to the electric component through which we need to find the voltage drop.

Question 25.

In parallel combination, the total resistance of the circuit becomes ___the individual resistances.

either less than or more than
equal to
more than
less than

Discuss Question

Answer: Option D. -> less than
:
D

When resistors are connected in parallel, the equivalent resistance is less than the lowest resistance in the circuit.
Proof is as follows:
As we know when $R_{1}, R_{2}, R_{3} . . . R_{n}$ resistors are connected in parallel circuit, the equivalent resistance of the circuit is
$\frac{1}{R_{e q}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} . . . \frac{1}{R_{n}}$
$\frac{1}{R_{e q}} \geq \frac{1}{R_{i}} \forall i \in {1, 2, 3, . . . ., n}$
$⟹ R_{e q} \leq R_{i}$

Question 26.

Three resistances each of 4 Ohm are connected in the form of an equilateral triangle. The effective resistance between any two corners is:

$\frac{3}{8} O h m$
$\frac{8}{3} O h m$
$8 O h m$
$12 O h m$

Discuss Question

Answer: Option B. ->

\frac{8}{3} O h m

:
B

Two in series = 8 Ohm

This 8 Ohm will be parallel to 4 Ohm which gives a resultant = ( $\frac{4 \times 8}{4 + 8}) = (\frac{8}{3}) O h m$ .

Question 27.

When the current in a conductor is doubled, keeping its resistance constant, the heat generated in the conductor will be:

double of the original
4 times of the original
3 times of the original
8 times of the original

Discuss Question

Answer: Option B. -> 4 times of the original
:
B

We know heat produced in a conductor is $H = I^{2} R t$ , where ' $I$ ' is the current flowing, ' $R$ ' is the resistance of wire and ' $t$ ' is the time for which current is flowing in a conductor.

When electrical resistance ' $R$ ' and time period ' $t$ ' is kept constant then, $H \propto I^{2}$ .
So, if the current is doubled, the heating effect of a current through a conductor becomes 4 times of the original.

Question 28.

An electric bulb is rated $220 V$ and $100 W .$ When it is operated at $110 V,$ the power consumed will be

$100 W$
$75 W$
$50 W$
$25 W$

Discuss Question

Answer: Option D. ->

25 W

:
D

Power consumed by the electric bulb, $P = \frac{V^{2}}{R}$ , where $V$ is the potential difference and $R$ is the electrical resistance.
Given for 1st case:
Voltage $V_{1} = 220 V$
and power consumed by bulb $P_{1} = 100 W,$
In the 2nd case:
Voltage of the bulb, $V_{2} = 110 V$
Power consumed by the bulb = $P_{2}$
Since the resistance is the same as it is the same bulb
$\frac{P_{1}}{P_{2}} = \frac{(V_{1})^{2}}{(V_{2})^{2}}$
$\frac{100}{P_{2}} = \frac{(220)^{2}}{(110)^{2}}$
$P_{2} = \frac{100 \times (110)^{2}}{(220)^{2}} = 25 W$
Power consumed when the bulb is operated at 110V = 25W

Question 29.

Two resistances of 100 Ω and 0 Ω are connected in parallel. The overall resistance will be:

100 Ω
50 Ω
25 Ω
0 Ω

Discuss Question

Answer: Option D. -> 0 Ω
:
D

Effective Resistance $(R_{e})$ when 2 resistors, let ( $R_{1} a n d R_{2}$ )are in parallel is given by $(R_{e})$ = $\frac{R_{1} \times R_{2}}{R_{1} + R_{2}}$

Given :
$R_{1} = 100 Ω$
$R_{2} = 0 Ω$
$(R_{e}) = \frac{100 \times 0}{100 + 0} = 0$

Question 30.

According to the convention, the direction of the flow of electric current is opposite to the direction of the flow of _______.

electrons
protons
neutrons
atoms

Discuss Question

Answer: Option A. -> electrons
:
A
Electric current is defined as the amount of charge flowing through a cross-section area per unit time. It's direction is conventionally taken opposite to the direction of flow of electrons.