PRACTICE
PAPER
CHAPTER 04 ELECTRICITY:
MAGNETIC
AND
HEATING
EFFECTS
SUBJECT: SCIENCE MAX. MARKS : 40
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CLASS : VIII DURATION : 1½ hrs
General Instructions:
(i).
All questions are compulsory.
(ii). This question paper contains
20 questions divided into five Sections
A, B, C, D and E.
(iii).
Section A comprises of 10 MCQs of
1 mark each. Section B comprises of 4
questions of 2 marks each. Section C
comprises of 3 questions of 3 marks
each. Section D comprises of 1 question of 5 marks each and Section E comprises of 2 Case Study
Based Questions of 4 marks each.
(iv). There is no overall choice.
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SECTION –A
Questions 1 to 10 carry 1 mark each.
1. 1. A student connects a simple
circuit with an electric cell and a wire. She places a magnetic compass near the
wire. Which of the following observations indicates that electric
current is flowing in the
wire?
(a) The wire becomes hot.
(b)
The magnetic compass
needle deflects from its original
direction.
(c) The compass needle does not move at all.
(d)
The wire attracts
small pieces of
paper.
2. 2 Which of the following household appliances works
on the principle of the heating effect
of electric current?
(a) Electric
fan (b) Loudspeaker (c) Electric
iron (d) Electromagnet
3. 3.A student makes an electromagnet by winding a coil of wire around an iron nail and connecting
it to a cell. She notices that the electromagnet can only pick up a few paper
clips. What is the most effective way to make the electromagnet stronger?
(a)
Use a longer iron nail. (b) Use a thinner
wire.
(c) Increase
the number of turns of the coil. (d) Change
the direction of the current.
4. 4. The Voltaic cell is named after which Italian
scientist who believed electricity came from the combination of metals and liquid, not
from a dead frog's leg?
(a) Luigi Galvani (b) Hans Christian Oersted
(c) Alessandro Volta (d) Isaac Newton
5.
An electromagnet is a temporary
magnet. Which of the following
conditions must be met for it to function as a magnet?
(a)
The circuit must be open.
(b) An electric current must flow through
the coil.
(c) A permanent bar magnet
must be placed nearby.
(d)
The wire must be made of a non-conducting material.
6. Which of the following
statements is true about the heating effect
of electric current?
(a) It is always a problem and a source
of energy loss.
(b)
It forms the basis of devices like an electric
stove and an electric kettle.
(c) It is only observed
in wires with high resistance.
(d)
It is the same as the magnetic
effect of electric
current.
7. Why do household circuits
have safety devices
in place?
(a) To increase the magnetic
field. (b) To minimize the heating effect
of electric current.
(c) To make the circuit more decorative. (d) To make the circuit
reusable.
8. What is the function
of the electrolyte in a Voltaic cell?
(a) It acts as a negative electrode.
(b) It produces electricity by chemical reaction
with the electrodes.
(c) It acts as an insulator.
(d)
It holds the two electrodes apart.
In the following questions 9 and 10, a statement of assertion (A) is followed by a statement of Reason (R). Choose the correct answer
out of the following choices.
(a) Both A and R are true and R is the correct explanation of A.
(b)
Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d)
A is false but R is true.
9. Assertion (A): A nichrome wire is a good conductor of electricity.
Reason (R): Nichrome wire offers higher
resistance and generates more heat compared
to a copper wire of the same
size and length.
1010.
Assertion
(A): The strength
of an electromagnet can be increased
by using a battery with more
cells.
Reason (R): A battery with more cells provides
a larger current, which creates
a stronger magnetic field.
SECTION – B
Questions 11 to 14 carry 2 marks each.
11.
Why does a compass needle deflect when placed near a
current-carrying wire, but
return to its original position when the current is stopped?
12. What is an electromagnet? List two of its practical applications.
13. How does the heating
effect of electric
current cause an incandescent lamp to glow?
1414.
Explain why a dry cell is considered a "single use" cell, while a rechargeable battery can be used multiple
times.
SECTION – C
Questions 15 to 17 carry 3 marks each.
15. State the factors that affect the amount of heat generated
in a wire due to electric current.
16. Describe the key components of a Voltaic
cell and explain
how it generates electricity.
17. A student makes an
electromagnet and finds its poles by using a magnetic compass. What would
happen to the poles of the
electromagnet if the direction of the current flowing through the coil is reversed? Justify your answer.
SECTION – D
Questions 18 carry 5 marks each.
18.
Explain the magnetic
effect of electric
current. How can the strength
of the magnetic field produced by a current-carrying coil be
changed? Describe two ways to do this.
SECTION – E (Case
Study Based Questions)
Questions 19 to 20 carry 4 marks each.
19. Case Study-1:
The Recycling Plant
Crane
In a bustling
recycling plant, a large crane operator, named Arjun, controls a powerful
lifting electromagnet to sort and move heavy metal waste. He uses a switch in
his control cabin to turn the magnet on and off. When he turns the switch ON,
the electromagnet attracts and lifts huge pieces of scrap metal. As he moves
the crane over the correct collection bin, he turns the switch OFF, and the metal
pieces fall cleanly
into place. This process is highly efficient and safe, allowing the plant to handle large
quantities of metal waste quickly and effectively.
(i) What is the function
of the switch in Arjun's
control cabin? [1]
(ii) Why do the metal pieces fall when Arjun turns the switch OFF? [1]
(iii) Why is an iron core used in lifting
electromagnets? [1]
(iv) Can the lifting electromagnet lift a heavy piece of plastic? Justify
your answer. [1]
20.
Case Study-2: The Lemon Battery
Experiment
Riya and her
friends are trying to make a simple electric cell using lemons
as part of their science project. They insert a
copper strip and an iron nail into a lemon, ensuring the two metals do not
touch. They connect the lemon to an
LED. The LED glows dimly. Riya is fascinated and
realizes that the lemon
juice acts as a crucial
component of the cell. She notes down that a chemical reaction is taking place inside the lemon
to produce electricity.
(i) In the lemon cell, what is the role of the lemon juice?
[1]
(ii)
What would happen
if Riya replaced
the lemon juice with pure water? Why? [1]
(iii) Why did the LED glow dimly?
[1]
(iv)
What components of this lemon cell can be compared to
the electrodes and electrolyte of a Voltaic cell? [1]
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