NCERT Solutions for Class 7 Science Curiosity Chapter 3: Electricity: Circuits and Their Components by PW

Understanding electricity involves more than knowing how a circuit works. Questions about heating, magnetism, electromagnets and electric cells often require you to interpret experiments, diagrams and observations carefully.

It can also be difficult to connect concepts such as electrolytes, nichrome wires and magnetic effects with their practical applications. These topics become easier when the role of electric current and its different effects are understood clearly.

NCERT Solutions Class 7 Science Curiosity Chapter 3 Solutions provide clear answers to textbook questions on circuits, electromagnets, Voltaic cells and the heating and magnetic effects of electric current. They explain activities and applications in simple terms, helping you understand the concepts and apply them to different question types.

Class 7 Science Chapter 3 Solutions

The following questions cover important concepts and activities related to electric current, electromagnets, heating effects and magnetic effects.

Electricity Circuits and Their Components Question Answers

Q1. Can we use electric current to make a magnet?

Answer: Yes.

The magnetic effect of electric current can be used to make a magnet.

When electric current passes through a conducting wire coiled around a metal nail or rod, the nail or rod becomes a magnet while the current is flowing. When the current stops, the nail or rod loses its magnetic force.

Q2. Does an electromagnet also have two poles like a bar magnet?

Answer: Yes.

An electromagnet has two poles, just like a bar magnet:

• North pole

• South pole

When current passes through a wire coiled around an iron nail, one end becomes the North pole and the other becomes the South pole. The deflection of a compass needle near the two ends can be used to identify the magnetic effect.

Q3. Are electromagnets also used in real life for lifting objects?

Answer: Yes.

Electromagnets are used in factories and scrap yards to move, lift and sort heavy metal objects.

How does an electromagnetic crane work?

1. The electromagnet is attached to a crane.

2. The operator switches ON the current.

3. The electromagnet attracts and lifts magnetic metal objects.

4. The crane moves the objects to another location.

5. The operator switches OFF the current.

6. The magnetic field disappears and the objects are released.

Q4. While doing the activity for the electromagnet, why did the wire ends get warm?

Answer:

The wire ends become warm when electric current flows through the wires for some time. This happens because of the heating effect of electric current.

The conductor offers resistance to the flow of current. As a result, some electrical energy is converted into heat energy, which warms the wire.

Q5. Can we make our own Voltaic cell using easily available materials?

Answer: Yes.

A simple Voltaic cell can be made using:

• Fresh lemons

• Iron nails

• Copper wires or strips

• An LED to check the current

Procedure:

1. Insert one iron nail and one copper strip into each lemon.

2. Connect the copper strip of the first lemon to the iron nail of the second lemon.

3. Continue connecting the copper strip of one lemon to the iron nail of the next lemon.

4. Connect the first iron nail to the negative terminal of the LED.

5. Connect the last copper strip to the positive terminal of the LED.

6. If the LED glows, the Voltaic cell is working.

Q6. Fill in the blanks

(i) The solution used in a Voltaic cell is called ________.

Answer: Electrolyte

(ii) A current-carrying coil behaves like a ________.

Answer: Magnet

Q7. Choose the correct option

(i) Dry cells are less portable compared to Voltaic cells. True/False

Answer: False

Reason: Voltaic cells are less portable because they use a liquid electrolyte.

(ii) A coil becomes an electromagnet only when an electric current flows through it. True/False

Answer: True

A current-carrying coil produces a magnetic effect and behaves like an electromagnet.

(iii) An electromagnet using a single cell attracts more iron paper clips than the same electromagnet with a battery of 2 cells. True/False

Answer: False

A battery of 2 cells can provide a stronger current, making the electromagnet stronger.

Q8. An electric current flows through a nichrome wire for a short time. Consider:

(i) The wire becomes warm.
(ii) A magnetic compass placed below the wire is deflected.

Which option is correct?

A. Only (i) is correct
B. Only (ii) is correct
C. Both (i) and (ii) are correct
D. Both are incorrect

Answer: C. Both (i) and (ii) are correct.

Reason:

• Current produces a heating effect, so the nichrome wire becomes warm.

• Current also produces a magnetic effect, causing the compass needle to deflect.

Q9. Match the items in Column A with Column B

Q10. Nichrome wire is commonly used in electrical heating devices because it:

(i) is a good conductor of electricity.
(ii) generates more heat for a given current.
(iii) is cheaper than copper.
(iv) is an insulator of electricity.

Answer: (ii) Generates more heat for a given current.

Nichrome is suitable for heating devices because it produces considerable heat when electric current passes through it.

Q11. Why are electric heating devices often considered more convenient than traditional heating methods?

Traditional methods include burning firewood or charcoal.

Answer:

Traditional heating methods can be less convenient because:

1. They require more storage space for firewood or charcoal.

2. Burning produces smoke, which can cause eye irritation and breathing problems.

3. Burning firewood and charcoal releases gases such as carbon dioxide and carbon monoxide.

4. These gases contribute to air pollution.

Electric heating devices such as heaters and electric stoves:

• Require less storage space.

• Do not produce smoke during normal use.

• Avoid the same direct indoor smoke pollution associated with burning firewood or charcoal.

Q12. Look at the figure. If the compass is placed near the coil, it deflects.

(i) Show the path of electric current.

Answer:

The current flows:

Positive terminal of cell → end A of coil → through the coil → end B → negative terminal of cell.

The direction is shown using arrows in the figure.

(ii) Why does the compass needle move when current flows?

Answer:

When electric current passes through the coil, the coil behaves like a magnet. The magnetic field produced by the coil affects the compass needle, causing it to deflect.

(iii) What happens if the battery terminals are reversed?

Answer:

Reversing the battery terminals reverses the direction of current. As a result:

• The poles of the electromagnet reverse.

• The compass needle deflects in the opposite direction.

Q13. Why does a lifting electromagnet stop lifting iron clips even though the wire is still warm?

Answer:

A conducting coil behaves as a magnet only while electric current is flowing through it.

When the current stops:

• The magnetic effect disappears.

• The electromagnet loses its ability to attract iron clips.

However, the wire can remain warm for some time because the current had previously produced heat through the heating effect of electric current. The wire takes some time to cool down.

Q14. In which case will the LED glow when the switch is closed?

Two setups are shown:

• (a): Iron nail and copper strip placed in lemon juice

• (b): Iron nail and copper strip placed in pure water

Answer: Case (a).

Reason:

Lemon juice acts as an electrolyte because it contains substances that allow electric current to pass through the liquid.

In case (b), pure water does not act as an effective electrolyte in this setup. Therefore, the LED glows in case (a).

Q15. Neha keeps the coil the same way as in Activity 4.4 but slides the iron nail out, leaving only the coiled wire. Will the coil still deflect the compass? Will the deflection be more or less than before?

Answer: Yes, the coil will still deflect the compass.

A current-carrying coil itself produces a magnetic field, so it can deflect the compass.

However:

• With the iron nail inside, the magnetic strength is greater.

• When the iron nail is removed, the electromagnet becomes weaker.

• Therefore, the compass deflection will be less than before.

NCERT Solutions for Class 7 Science Curiosity Chapter 3 PDF

Use the Class 7 Science Curiosity Chapter 3 Solutions PDF to review important questions and answers on electricity, circuits, electromagnets, Voltaic cells and the effects of electric current.

Why Choose NCERT Class 7 Science Chapter 3 Solutions by PW?

The NCERT Class 7 Science Chapter 3 Solutions by PW explain electricity through clear answers, practical examples and activity-based questions. They can help children understand the concepts of electric current and its effects while preparing for textbook exercises.

• Understand the Magnetic Effect of Current: Learn how a current-carrying coil produces a magnetic field and how this effect is used to create electromagnets.

• Learn the Working of Electromagnets: Understand how coils, electric current and iron cores work together and why an electromagnet loses its magnetic effect when the current stops.

• Explore the Heating Effect of Current: Understand why wires become warm when current flows through them and why materials such as nichrome are used in heating devices.

• Understand Voltaic Cells and Electrolytes: Learn how a simple cell generates electricity through chemical reactions and why an electrolyte is important in the process.

• Relate Concepts to Everyday Applications: Connect textbook concepts with examples such as electromagnetic cranes, electric irons and other electrical heating devices.

• Practise Activity-Based Questions: Work through questions involving circuits, compass deflection, battery connections and practical observations.

• Develop Scientific Reasoning: Use observations from experiments and activities to explain magnetic effects, heating effects and changes in circuit behaviour.

From simple circuit activities to practical uses of electromagnets and heating devices, Chapter 3 shows how electric current produces different effects. The NCERT Class 7 Science Chapter 3 Solutions provide clear explanations for questions on Voltaic cells, magnetic effects, heating effects and circuit-based activities. Revising these concepts can make it easier for children to connect classroom learning with everyday electrical applications.

Related Resources

• CBSE Class 7 Science Syllabus

• CBSE Class 7 Science NCERT Solutions

• CBSE Class 7 Science Sample Papers

• CBSE Class 7 Science Notes