⚡✨ Class 8 Science
Curiosity Chapter 4
🔌
Electricity: Magnetic and Heating Effects
🎯 Keep
the Curiosity Alive
1. Fill in the blanks:
(i) The solution used in a Voltaic cell is called ________.
(ii) A current carrying coil behaves like a ________.
👉 See
Answer:
(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.
👉 See
Answer:
❌ False
👉 Dry cells are more
portable 🎒, while
Voltaic cells are bulky
(ii) A coil becomes an electromagnet only when
electric current flows through it.
👉 See
Answer:
✔️ True
👉 Current flow →
magnetic field → electromagnet 🧲
(iii) An electromagnet, using a single cell,
attracts more iron paper clips than the same electromagnet with a battery of 2
cells.
👉 See
Answer:
❌ False
👉 More cells 🔋 →
stronger current → stronger magnet 💪
⚡ Class
8 Science Curiosity Chapter 4 Question 3 and 4
3. An electric current flows through a nichrome
wire for a short time.
(i) The wire becomes warm.
(ii) A magnetic compass placed below the wire is deflected.
Choose the correct option:
(a) Only (i) is correct
(b) Only (ii) is correct
(c) Both (i) and (ii) are correct
(d) Both (i) and (ii) are not correct
👉 See
Answer:
✔️ (c) Both (i) and (ii) are
correct
💡
Explanation:
- 🔥
Heating effect → wire becomes warm
- 🧲
Magnetic effect → compass deflects
4. Match the items in Column A with those in
Column B:
📊 Given:
|
Column A
|
Column B
|
|
(i) Voltaic cell
|
(a) Best suited for electric heater
|
|
(ii) Electric iron
|
(b) Works on magnetic effect of electric current
|
|
(iii) Nichrome wire
|
(c) Works on heating effect of electric current
|
|
(iv) Electromagnet
|
(d) Generates electricity by chemical reactions
|
👉 Answer:
|
Column A
|
Column B
|
|
(i) Voltaic cell
|
(d) Generates electricity by chemical reactions ⚗️
|
|
(ii) Electric iron
|
(c) Works on heating effect 🔥
|
|
(iii) Nichrome wire
|
(a) Best suited for electric heater 🔥
|
|
(iv) Electromagnet
|
(b) Works on magnetic effect 🧲
|
⚡ Class
8 Science Curiosity Chapter 4 Question 5, 6 and 7
5. 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.
👉 See
Answer:
✔️ (ii) generates more heat
for a given current 🔥
💡
Reason:
👉 Nichrome has high
resistance → produces more heat
6. Electric heating devices (like an electric
heater or stove) are often considered more convenient than traditional heating
methods (like burning firewood or charcoal). Give reason(s) to support this
statement considering societal impact.
👉 See
Answer:
🔥
Advantages of electric heating devices:
• 🚫
Smokeless and clean → no pollution
• 🎛️ Easy to operate → simple
ON/OFF control
• ⚡ More efficient → energy
directly converts into heat
• ⏱️ Saves time and effort
• ❤️ Safer for health and
environment
🎯 Final
Line
⚡
Electricity = Power of Modern Life
👉
Heating + Magnetic effects = Everyday Applications 🔌
7. Look at Fig. 4.4a. If the compass placed near the coil
deflects: (i) Draw an arrow on the diagram to show the path of the electric
current.. (ii) Explain why the compass needle moves when current flows. (iii)
Predict what would happen to the deflection if you reverse the battery
terminals.
See Answer(i) The compass needle moves because the current
carrying coil produces a magnetic field which affects the compass.
(ii) If battery terminals are reversed, the direction of current reverses, so
the deflection of compass needle also reverses.
Class 8 Science Curiosity Chapter 4 Question 8,
9 and 10
8. Suppose Sumana forgets to move the switch of her lifting
electromagnet model to OFF position (in introduction story). After some time,
the iron nail no longer picks up the iron paper clips, but the wire wrapped
around the iron nail is still warm. Why did the lifting electromagnet stop
lifting the clips? Give possible reasons.
See Answer The cell/battery has become weak or exhausted, so it cannot provide
enough current to make the electromagnet strong.
However, the weak current still produces some heating in the wire, making it
warm, even though it is not strong enough to lift clips.
9. In Fig. 4.11, in which case will the LED glow when the
switch is closed?
See Answer Case (a): Iron nail + Lemon juice + Copper strip → LED
will glow (because lemon juice acts as an electrolyte).
Case (b): Iron nail + Pure water + Copper strip → LED
will not glow (pure water is a poor conductor).
10. Neha keeps the coil exactly the same as in Activity 4.4
but slides the iron nail out, leaving only the coiled wire. Will the coil still
deflect the compass? If yes, will the deflection be more or less than before?
See Answer Yes, the coil will still deflect the compass because a current
carrying coil produces a magnetic field.
But the deflection will be less because without the iron core the electromagnet
is weaker.
Class 8 Science Curiosity Chapter 4 Question 11
11. We have four coils, of similar shape and size, made up
from iron, copper, Aluminium and Nichrome as shown in Fig. 4.12.
When current is passed through the coils, compass needles
placed near the coils will show deflection.
(i) Only in circuit (a)
(ii) Only in circuit (a) and (b)
(iii) Only in circuit (a), (b), and (c)
(iv) In all four circuits
See Answer(iv) In all four circuits (Because all these materials are conductors
and when current flows, they produce a magnetic effect).
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