Electricity Important Questions Class 10 Science with Solutions

Chapter 11: CBSE Class 10 Electricity is a very important part of the Class 10 Science syllabus CBSE 2025, bounding the crucial principles that govern the flow of electric charge, the relationship between various electrical quantities, and the practical applications of electrical concepts. Understanding this chapter is key to mastering the physics behind everyday electrical systems and preparing effectively for the exams. Let’s break down the key topics and concepts of this chapter for class 10 students and make studying physics a little easier.

Science Class 10 Electricity Important Questions contain various questions that are useful for students even in their competitive examinations like JEE & NEET. In this chapter, you learn about the various properties and uses of Electricity. You also become aware of the numerous important precautions you need to keep in mind while dealing with electricity and electrical appliances.

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Chapter 11 Electricity: Important Questions

1. Read the information given below and answer four out of five following questions.

Suresh bought a packet of 100 LEDs to make his own lights for decoration in his house. The packet on the LEDs had the following printed on a label:

LED 2835, 0.2 W, 30 Lumens, 3 V

To understand how he should connect the LEDs, he referred to the following circuit diagram on a website.

1.1 Which of the following describes how the LEDs are connected in the circuit diagram? 

a. all in series 

b. all in parallel

c. 8 each in a series combination, and the two combinations in parallel

d. 8 each in a parallel combination, and the two combinations in series

Answer: 

(C) 8 each in a series combination, and the two combinations in parallel.

Explanation:

In the circuit diagram, LEDs are grouped into two rows. Each row contains 8 LEDs connected in series, and the two rows are connected in parallel to the mains supply.

1.2  If the LED marked 'LED 2' in the diagram stops working, which other LEDs will also stop working?

(Note: When an LED stops working, current cannot flow across it.)

a. only LED 3 to LED 8

b. only LED 3 to LED 8 and LED 1

c. all the other LEDs in the circuit

d. none of the other LEDs in the circuit

Answer: 

(B) Only LED 3 to LED 8 and LED 1.

Explanation:

In a series connection, if one LED stops working, the entire current path for that series segment is broken. Therefore, all LEDs in that specific series combination (LEDs 1 to 8) will stop working, while LEDs in the other parallel branch (LEDs 9 to 16) will continue to work.

1.3  Suresh decided to connect all the LEDs in his lights in a series combination.

How many LEDs will he need to connect if he is going to connect the lights to a 240 V mains supply so that the LEDs work at their power rating?

a. 16

b. 80

c. 240

d. 1200

Answer: (B) 80 LEDs.

Explanation:

Each LED operates at 3 V. In a series connection, the total voltage is divided among all the LEDs.

Number of LEDs= Total Voltage/Voltage per LED

= 240/3

=80

1.4  What will happen if he connects 100 LEDs, all in a parallel combination, to the 240 V mains supply?

a. Each LED will work as expected since the available voltage is more than 3 V.

b. Each LED will have a potential difference of 220 V and therefore they will get damaged.

c. Each LED will glow but the ones closer in the circuit to the main supply will glow brighter.

d. Each LED will have a potential difference of 2.4 V across it and therefore will glow dimmer than normal.

Answer: 

(B) Each LED will have a potential difference of 220 V and therefore they will get damaged.

Explanation:

In a parallel connection, each branch gets the full voltage of the mains supply. If the LEDs are directly connected to a 240 V supply instead of their rated 3 V, the LEDs will burn out due to excessive voltage.

1.5  How much current is each LED expected to draw when used according to the ratings given in the label?

a. 0.067 A

b. 0.600 A

c. 10 A

d. 15 A

Answer:

‍(A) 0.067 A

Explanation:

The power rating of each LED is 0.2 W, and the voltage rating is 3 V. Using the formula:

I = P/V

= 0.2 / 3

=0.067A

2. The diagram below shows how Amita had connected a circuit to verify Ohm's law.

(a) Identify which of the devices in the circuit is an ammeter. Justify your answer.

(b) Draw a circuit diagram with appropriate symbols for the circuit shown in the diagram above.

(c) Amita forgot to put a switch in the circuit. During the experiment, the wire labelled 'Unknown resistor' became hot. The resistivity of the material of the wire increases with temperature. Draw two potential difference vs current graphs (in the same diagram):

(i) as expected by Amita,

(ii) as based on actual observation she would make.

Answer: 

In the circuit:

• Meter 1 is connected in series with the circuit, which is a requirement for an ammeter (since it measures the current flowing through the circuit).
• Meter 2, on the other hand, is connected in parallel across the unknown resistor, making it a voltmeter (since it measures the potential difference).

Thus, Meter 1 is the ammeter because it is positioned to measure the total current flowing through the circuit.

(b) 

(c)

Graph expected by Amita (Ohm's law):

Ohm's law states V=IR, where RRR is constant.

The graph of potential difference (V) vs current (I) would be a straight line passing through the origin, indicating a constant resistance.

Graph based on actual observation:

As the wire heats up, its resistivity increases, causing the resistance R to increase with temperature.

The graph would curve downward as the current decreases for a given voltage, deviating from the straight line.

3. An incandescent bulb works on the heating effect of electric current. When a current passes through the filament of a bulb it heats the filament to a high temperature which causes the filament to glow.

The graph below shows the variation in the current through a bulb immediately after it is switched on. The current decreases from 1 A at time t=0 to 0.5 A at t=t,. The voltage of the power supply is 200 V and remains constant throughout.

(a) Based on the graph, state how the resistance of the bulb filament changes as the temperature increases from time t=0 to t=t₁.

(b) What is the power consumed by the bulb when it is glowing at its full brightness?

Answer: (a)

At t=0, I=1A,

R=V/I

200/1

200Ω.

At t=t₁, I=0.5A,

R=V/I

200/0.5

400Ω.

(b)

P=V×I

=200×0.5

=100W.

4. Observe the circuit shown below. All the three switches are open.

Identify the switch/switches that on being closed will cause the fuse to blow.

Answer: 

Switch 1 and Switch 3, when closed together, will cause the fuse to blow due to a short circuit.

Closing only Switch 1 and Switch 2 may also blow the fuse if the bulb's resistance allows excessive current, but this depends on the fuse's rating and the bulb's specifications.

5. You are given three identical 10 ohm resistors and a 12 V cell.

Draw the circuit diagram to show how the resistors can be connected with the 12 V cell so that the total heat produced in the circuit is the MINIMUM.

Answer: 

To minimize the heat produced in the circuit, the total current flowing through the circuit should be minimized. This is achieved by maximizing the total resistance of the circuit. To do this, the three resistors should be connected in series because the total resistance of resistors connected in series is the sum of their individual resistances, which is higher than in any other configuration.

6. Study the circuit diagram given below. You are given one extra resistor. By drawing a new circuit diagram, show how you can connect the extra resistor to increase the reading on the ammeter in the circuit below.

Answer: 

To increase the current in the circuit, you need to reduce the overall resistance. This can be done by connecting the extra resistor in parallel with the existing resistors in the circuit. When resistors are connected in parallel, the equivalent resistance decreases.

This reduces the total resistance and, according to Ohm's Law (I=V/R), increases the current flowing through the circuit.

7. Priya has a copper wire and an aluminium wire of the same length.

Can the electrical resistance of the two wires be the same? Justify your answer.

Answer: 

Yes, the electrical resistance of the copper wire and the aluminum wire can be the same, but certain conditions must be satisfied.

The resistance of a wire is given by the formula:

R=ρ (L/A)

Since the two wires have the same length (L), the resistance depends on their resistivity (ρ) and cross-sectional area (A).

Copper has a lower resistivity (ρ_copper=1.68×10⁻⁸ Ω m} than aluminum (ρ_aluminum=2.82×10⁻⁸ Ω m}. To achieve the same resistance, the aluminum wire must have a larger cross-sectional area than the copper wire to compensate for its higher resistivity.

A_aluminum​=A_copper​⋅ρ_copper​/ρ_aluminum​​

Since ρ_aluminum>ρ_copper​, the aluminum wire's cross-sectional area (A_aluminum​) must be larger than that of the copper wire (A_copper).

The electrical resistance of the copper wire and aluminum wire of the same length can be made equal if the aluminum wire has a larger cross-sectional area than the copper wire, proportional to the ratio of their resistivities.

Key Concepts in Electricity CBSE Class 10 Ch 11:

Electricity is a fundamental concept in physics, essential for understanding how electrical circuits work. These few concepts given below are the foundation for understanding electrical energy transfer and its practical applications. Let’s know more about them:

Electric Current:

• Electric current is the flow of electric charge, typically carried by electrons in a conductor.
• The unit of electric current is ampere (A), which is defined as the amount of charge passing through a conductor per second.

Voltage (Potential Difference):

• Voltage, or potential difference, is the energy required to move a unit charge from one point to another in an electric circuit.
• It is measured in volts (V) and is responsible for pushing the current through a conductor.

Resistance:

• Resistance is the property of a material that resists the flow of electric current. It depends on factors like the material’s nature, length, cross-sectional area, and temperature.
• The unit of resistance is ohms (Ω).

Ohm’s Law:

• Ohm’s Law is the foundation of understanding electrical circuits. It states that the current flowing through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.
• Mathematically, V = IR, where V is voltage, I is current, and R is resistance.

Important Topics in Chapter 11 CBSE Class 10

Chapter 11 of CBSE 10 Class covers important topics that are very likely to be asked in the CBSE Board Exam 2025. Understanding these topics helps students solve problems related to electricity quite easily. These concepts are important for both theoretical understanding and practical problem-solving:

Resistivity and its Dependence:

• Resistivity is the property of a material that determines its resistance. Materials with low resistivity, like copper, are good conductors, while those with high resistivity, like rubber, are insulators.
• Formula for resistance:
  R = ρL / A
  Where R is resistance, ρ is resistivity, L is the length, and A is the cross-sectional area.

Heating Effect of Electric Current:

• When electric current flows through a conductor, it produces heat. This is known as the heating effect of current.
• This principle is used in devices like electric irons, toasters, and bulbs. The heat produced depends on the current, resistance, and time for which the current flows.
• Formula: H = I²Rt, where H is the heat produced, I is the current, R is resistance, and t is time.

Power in Electric Circuits:

• Power is the rate at which electrical energy is consumed or converted into another form of energy (like heat or light).
• Formula: P = IV (where P is power, I is current, and V is voltage) or P = I² R. Power is measured in watts (W).

Combination of Resistors: Resistors can be connected in two ways: series or parallel.

• In series, the total resistance increases, and the current is the same through all components.
• In parallel, the total resistance decreases, and the voltage is the same across all components.

Applications of Electricity in Daily Life

Electricity powers many aspects of our daily life, from household appliances to transportation systems. This chapter highlights how concepts like power, resistance, and the heating effect of current apply to real-life devices like:

1. Electric Appliances: Electrical concepts are applied in everyday appliances like refrigerators, air conditioners, and washing machines. Understanding the power consumption and efficiency of these devices is important.
2. Power Transmission: High-voltage transmission lines carry electricity over long distances. The principles of resistivity and power loss are critical to the efficient transmission of electrical energy.
3. Electric Circuits in Vehicles: Vehicles use a combination of series and parallel circuits to power various electrical components such as headlights, air conditioning, and infotainment systems.
4. Safety in Electrical Circuits: Fuses, circuit breakers, and earthing are safety devices used to prevent overloading and protect electrical appliances and individuals from potential hazards.

Tips for Preparing Chapter 11 Class 10 CBSE: Electricity

To prepare for this chapter, focus on understanding you need to revise key concepts and relate them to real-life applications. By following the tips given below, it can be really helpful and easy for students to cover up the chapter Electricity:

Understand Basic Concepts: Focus on the fundamentals of current, voltage, resistance, and Ohm’s law. Understand the relationship between current, voltage, and resistance using the formula V=IR (Ohm’s Law).

Learn the Units and Their Conversion: Memorise the units for electrical quantities—amperes (A) for current, volts (V) for voltage, ohms (Ω) for resistance, and watts (W) for power. Practice converting between units, like milliamperes (mA) to amperes (A) and millivolts (mV) to volts (V).

Practice Circuit Diagrams: Draw and label different circuit diagrams, including series and parallel circuits. Understand how to calculate total resistance, current, and voltage in series and parallel circuits.

Work on Numericals: Solve problems involving Ohm’s Law, power calculation (P=VIP=VIP=VI), and resistances in series and parallel. Practice questions related to heating effects of current and their applications.

Understand Electrical Safety: Learn the importance of fuses, circuit breakers, and earthing in electrical circuits for safety. Study the principles behind electric power transmission and how resistivity plays a role in efficiency.

Revise Key Formulas: Ensure you are comfortable with important formulas such as P=I2R, V=IR, and RTotal for series and parallel circuits.

Solve Sample Papers and Past Year Questions: Practice with sample papers and past CBSE exam questions to get familiar with the types of problems that may appear in the exam.

Chapter 11 Electricity is really important for understanding the fundamental principles of electric current, resistance, and power. It has numerous real-world applications, from household appliances to the transmission of electrical power. By mastering the core concepts, practicing problems, and understanding their practical implications, students can build a solid foundation for this chapter. Whether through solving numerical problems or drawing circuit diagrams, consistent practice and application of the formulas will ensure success in exams. Happy learning!

We hope that you practice the above Electricity Class 10 Imp Questions and achieve your dream marks.

All the best!