Electricity PYQ Class 10

CBSE

1
(a) A wire of resistance R is cut into three equal parts. If these three parts are then joined in parallel, calculate the total resistance of the combination so formed.
  OR
(b) Define electric power. When do we say that the power consumed in an electric circuit is 1 watt?

[2 marks]

2

Consider the following electric circuit :

Calculate the values of the following:

(a) The total resistance of the circuit

(b) The total current drawn from the source

(c) Potential difference across the parallel combination of 10 $\Omega$ and 15 $\Omega$ resistors

[3 marks]

3

(a) 

 Write the relationship between resistivity and resistance of a cylindrical conductor of length $l$ and area of cross-section $A$. Hence derive the SI unit of resistivity.
(b)  Why are alloys used in electrical heating devices?

[3 marks]

4

(A) Show how you would connect three resistors each of resistance 6 $\Omega$, so that the combination has a resistance of 9 $\Omega$. Also justify your answer.

OR

(B) In the given circuit calculate the power consumed in watts in the resistor of 2 $\Omega$:

Screenshot 2026-03-27 at 2.48.12 PM

[2 marks]

5
(A)
(i) Define electric power. Express it in terms of potential difference (V) and resistance (R).
(ii)

An electric oven is designed to work on the mains voltage of 220 V. This oven consumes 11 units of electrical energy in 5 hours. Calculate:

(a) power rating of the oven
(b) current drawn by the oven
(c) resistance of the oven when it is red hot
  OR
(B)
(i) Write the relation between resistance R and electrical resistivity $\rho$ of the material of a conductor in the shape of cylinder of length $l$ and area of cross-section A. Hence derive the SI unit of electrical resistivity.
(ii) The resistance of a metal wire of length 3 m is 60 $\Omega$. If the area of cross-section of the wire is $4 \times 10^{-7}\text{ m}^{2}$ calculate the electrical resistivity of the wire.
(iii) State how would electrical resistivity be affected if the wire (of part 'ii') is stretched so that its length is doubled. Justify your answer.

[5 marks]

6

If four identical resistors, of resistance 8 ohm, are first connected in series so as to give an effective resistance \( R_{s} \) and then connected in parallel so as to give an effective resistance \( R_{p} \) then the ratio \( \frac{R_{s}}{R_{p}} \) is

[1 mark]

7

In the following diagram, the position of the needle is shown on the scale of a voltmeter. The least count of the voltmeter and the reading shown by it respectively are:

Screenshot 2026-04-04 at 3.02.36 PM

[1 mark]

8

(a) An electric iron consumes energy at a rate of 880 W when heating is at the maximum rate and 330 W when the heating is at the minimum. If the source voltage is 220 V, calculate the current and resistance in each case.

(b) What is heating effect of electric current?

(c) Find an expression for the amount of heat produced when a current passes through a resistor for some time.

[5 marks]

9
(a)

Three resistors $R_{1}$, $R_{2}$ and $R_{3}$ are connected in parallel and the combination is connected to a battery, an ammeter, a voltmeter and a key. Draw suitable circuit diagram to show the arrangement of these circuit components along with the direction of current flowing.
(b)

Calculate the equivalent resistance of the following network:

[3 marks]

10
(a)
(i)

Define Electric Power and write its SI unit.
(ii)

Two bulbs rated $100\text{ W}; 220\text{ V}$ and $60\text{ W}; 220\text{ V}$ are connected in parallel to an electric mains of $220\text{ V}$. Find the current drawn by the bulbs from the mains.
  OR
(b)
(i)

State Joule's law of heating. Express it mathematically when an appliance of resistance $R$ is connected to a source of voltage $V$ and the current $I$ flows through the appliance for a time $t$.
(ii)

A $5 \Omega$ resistor is connected across a battery of $6\text{ volts}$. Calculate the energy that dissipates as heat in $10\text{ s}$

[3 marks]