Electricity - Magnetic and Heating effects solutions Class 8 Curiosity

🔍 Introduction

Electricity plays a major role in our daily lives. From lighting up our homes to running our gadgets, it’s everywhere! In this chapter, we explore how electricity produces both magnetic and heating effects and how we use them in real life.

Let’s dive into the in-text questions from the NCERT Curiosity textbook and understand each answer with clarity and examples. 🔋🔌

🔌 In-text Questions
Electricity: Magnetic and Heating Effects

1. If we don’t have an electric lamp while making an electric circuit with an electric cell, is there any other way to find out if current is flowing in the circuit?

Answer: Yes, we can use a magnetic compass. If it shows deflection near the wire, current is flowing. This happens due to the magnetic effect of electric current.

2. Is it possible to make temporary magnets? How can these be made?

Answer: Yes, temporary magnets or electromagnets can be made by wrapping an insulated copper wire around an iron nail and passing electric current through it.

3. How is heat generated in various electrical appliances?

Answer: Heat is generated due to the heating effect of electric current. When current passes through resistive materials like nichrome, it produces heat.

💡 Did You Know? This principle is used in devices like electric heaters and toasters.

4. How do we know if a cell or battery is dead? Can all cells be recharged?

Answer: A dead cell won't light a bulb or deflect a compass needle. Not all cells can be recharged — dry cells are non-rechargeable, while lithium-ion and NiMH cells are rechargeable.

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

Answer: Yes, electric current can create an electromagnet by passing it through a coil wrapped around a soft iron core.

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

Answer: Yes, just like a bar magnet, an electromagnet has both north and south poles depending on the direction of current.

7. Are electromagnets used in real life for lifting objects?

Answer: Yes, they are used in cranes to lift heavy scrap metal and in devices like electric bells and MRI machines.

8. Why do wire ends get warm while using an electromagnet?

Answer: Current passing through the wire faces resistance. This resistance converts some electrical energy into heat, warming the wire ends.

9. How does a battery generate electricity?

Answer: A battery generates electricity through chemical reactions that release electrons. These electrons flow in the circuit and provide electric energy.

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

Answer: Yes! A lemon battery can be made using a lemon, a copper strip, and a zinc nail. The lemon juice acts as the electrolyte.

🍋 Fun Fact: Multiple lemon batteries can even light up a small LED!

Exercise Questions – Keep the Curiosity Alive

1. Fill in the blanks:

(i) The solution used in a Voltaic cell is called electrolyte.
(ii) A current-carrying coil behaves like a magnet.

2. Choose the correct option:

(i) Dry cells are less portable compared to Voltaic cells. – False
(ii) A coil becomes an electromagnet only when electric current flows through it. – True
(iii) An electromagnet using a single cell attracts more iron clips than one using two cells. – False

3. An electric current flows through a nichrome wire:

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

Correct Option: (c) Both (i) and (ii) are correct

4. Match the items in Column A with Column B:

Column A	Column B
(i) Voltaic cell	(d) Generates electricity by chemical reactions
(ii) Electric iron	(c) Works on heating effect of electric current
(iii) Nichrome wire	(a) Best suited for electric heater
(iv) Electromagnet	(b) Works on magnetic effect of electric current

5. Why is nichrome wire used in heating devices?

Correct reasons:

(ii) generates more heat for a given current.

So, option (ii) is correct.

6. Why are electric heating devices considered convenient?

Electric heating devices like stoves and heaters are:

Cleaner than traditional methods (no smoke or ash)
More efficient and easier to control
Cause less environmental pollution
Safer and more reliable for indoor use

💡 Pro Tip: Using electricity for heating helps reduce deforestation caused by cutting wood for fuel.

7. Magnetic Effect Activity Based on Figure 4.4a

(i) Draw an arrow along the wire to show the direction of current (from positive to negative terminal).

(ii) The compass needle moves due to the magnetic field produced around the wire when current flows through it.

(iii) If the battery terminals are reversed, the direction of current changes. Hence, the magnetic field reverses, and the compass needle deflects in the opposite direction.

✨ Did You Know? Reversing the battery in a circuit also reverses the direction of magnetic field around the wire!

8. Why did the electromagnet stop lifting paper clips though the wire remained warm?

Possible reasons:

The battery is weak or discharged, so current is not strong enough.
Even though the wire is warm (indicating past current), the current has reduced or stopped due to low voltage.
Prolonged current may have demagnetized the iron nail temporarily.

⚠️ Did you know? Even if a wire is warm, it doesn’t always mean current is still flowing strongly!

9. In Fig. 4.11, in which case will the LED glow?

Answer: The LED will glow in Fig. 4.11 (a), because lemon juice is an electrolyte and allows current to pass. Pure water is a poor conductor and will not allow the LED to glow in (b).

10. If the iron nail is removed from the coil, will the compass still show deflection?

Answer: Yes, the coil will still deflect the compass because electric current produces a magnetic field. However, the deflection will be less than before because the iron nail enhances the magnetic field strength.

💡 Pro Tip: The presence of an iron core makes an electromagnet stronger.

11. Which coils will deflect the compass when current flows?

Correct Option: (iv) In all four circuits

Reason: All metals (iron, copper, aluminium, nichrome) conduct electricity. When current flows through any coil, a magnetic field is produced which causes deflection in a magnetic compass.

🧲 Did you know? The material of the coil doesn't affect the creation of a magnetic field, as long as current flows through it!

✨ Final Words

This completes our exploration of Electricity – Magnetic and Heating Effects. We learned about electromagnets, heating of wires, magnetic deflection, and how current behaves in different situations. Keep experimenting, keep observing – science is all around us!

Stay curious and stay charged up! 🔌⚡