Last Updated on August 2, 2024 by XAM CONTENT

Hello students, here you will find numerical problems on electricity with answers. These numericals on electricity are very useful for students studying in CBSE Class 10 or for anyone who wants to practice some problems on these topics.

Before we start solving the numerical problems, let’s see some important points and formulae. This will help you to solve the problems efficiently.

### Important Concept and Formulae

(1) If Q coulombs of charge flows through a conductor in t seconds, then current I is given by,

The instrument used to measure electric current is called ammeter.

(2) Ohm’s Law: According to Ohm’s law, the current flowing through a conductor is directly proportional to the potential difference across its ends, provided the temperature remains constant and the physical state of the conductor remains the same.

where R is constant, known as resistance of the conductor.

The property of a conductor due to which it opposes the flow of current through it, is called resistance.

(3) The resistance (R) is given by,

where ρ is called specific resistance or resistivity of the conductor.

When l = 1, A = 1, we have R = ρ. Thus, the resistivity of a conductor is the resistance of unit length and unit area of cross-section of the conductor.

(4) Series combination of resistances:

(5) Parallel combination of resistances:

(6) In case of a series combination of resistances, the combined resistance is greater than all the individual resistances. In case of a parallel combination of resistances, the combined resistance is smaller than the least individual resistance.

### Electricity Numerical Problems with Answers

Q.1. Three resistances, each equal to 5 Ω, are connected in series with a cell of 1.2 V. Find the magnitude of current in the circuits.

Ans. 0.08 A

Q.2. An electric bulb connected to a 220 V supply line draws a current of 0.05 A. Calculate the amount of coulombs per second flowing through the bulb.

Ans. 0.15 C/s

Q.3. The resistances of 5 Ω, 10 Ω and 15 Ω are connected in series and a potential difference of 1.5 V is applied across the extreme ends. Calculate the current passing through the circuit.

Ans. 0.05 A

Q.4. An equilateral triangle is formed with each side having a resistance of 2 Ω. What is the effective resistance across any side.

Ans. 4/3 Ω

Q.5. A battery of 6 V is connected in series with three resistors of 12 Ω, 6 Ω and 4 Ω as shown in Fig. is the current through each of the

resistors the same? Calculate the potential difference across each resistor.

Ans. 36/11, 18/11, 12/11 volt

Q.6. Fifty lamps each of resistance 100 Ω are connected in parallel across a 220 V main. Find (a) the power consumed in watts, and (b) the

cost of operating the lamps for 20 hours at 10 paise per kWh.

Ans. (a) 24,200 W, and (b) Rs. 48.40

Q.7. Three equal resistors connected in series across a source of e.m.f. together dissipate 10 W of power. What should be the power dissipated if the resistors are connected in parallel across the same e.m.f.?

Ans. 90 W

Q.8. A wire 150 cm long and diameter 1.0 mm is made of an alloy of resistivity 44 × 10^{–8} Ωm. What is the resistance of the wire?

Ans. 0.42

Q.9. A copper wire is stretched to double its length, keeping the volume same. If the original resistance of the wire is 4 Ω, What is the final

resistance?

Ans. 16 Ω

Q.10. If the wire has a resistance of 1.32 Ω, a length of 110 cm, and an area of cross-section of 0.00415 cm^{2}, find the resistivity of the material of which it is made.

Ans. 49.8 × 10^{–8} Ωm

We hope the given numerical problems on electricity helps you in your learning.

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