Important and HOT multiple choice questions for chapter 4-Electricity: Magnetic and Heating Effects in Class VIII (Subject-Science)
(A) Conceptual / Knowledge-Based
Q1. Which scientist discovered that electric current produces a magnetic effect?
a) Alessandro Volta
b) Hans Christian Oersted
c) Michael Faraday
d) James Clerk Maxwell
Ans: b) Hans Christian Oersted
Q2. The region around a current carrying wire where its magnetic effect can be felt is called:
a) Electromagnet
b) Magnetic field
c) Electric flux
d) Resistance zone
Ans: b) Magnetic field
Q3. A current-carrying coil of wire behaves like:
a) A resistor
b) A permanent magnet
c) An electromagnet
d) A battery
Ans: c) An electromagnet
Q4. Which of the following strengthens an electromagnet?
a) Reducing current
b) Using a copper core
c) Increasing number of turns in coil
d) Using plastic as core
Ans: c) Increasing number of turns in coil
Q5. The Earth’s magnetic field is caused due to:
a) Solar radiation
b) Rotation of Earth
c) Movement of liquid iron in Earth’s core
d) Gravitational pull
Ans: c) Movement of liquid iron in Earth’s core
Q6. Which metal wire is commonly used as a heating element?
a) Copper
b) Aluminium
c) Nichrome
d) Silver
Ans: c) Nichrome
Q7. The heating effect of electric current is due to:
a) Absence of resistance
b) Resistance of the conductor
c) Flow of magnetic field
d) Increase in voltage only
Ans: b) Resistance of the conductor
Q8. Which household device does not work on the heating effect of current?
a) Electric iron
b) Immersion rod
c) Electric fan
d) Room heater
Ans: c) Electric fan
Q9. A dry cell has its positive terminal at:
a) Zinc container
b) Carbon rod with metal cap
c) Both terminals outside
d) Electrolyte paste
Ans: b) Carbon rod with metal cap
Q10. Which type of battery is most common in laptops and phones?
a) Nickel-cadmium
b) Lead-acid
c) Lithium-ion
d) Zinc-carbon
Ans: c) Lithium-ion
(B) Competency-Based
Q11. In a science fair, a student makes an electromagnet using 20 turns of coil. Another student uses 40 turns of the same wire with the same cell. Whose electromagnet will be stronger?
a) First student
b) Second student
c) Both equal
d) Depends on compass
Ans: b) Second student
Q12. If you reverse the direction of current in an electromagnet, what will happen to its poles?
a) Poles disappear permanently
b) Poles remain unchanged
c) Poles reverse
d) Magnet becomes weak only
Ans: c) Poles reverse
Q13. A nichrome wire and a copper wire of same length and thickness are connected to identical cells. Which wire will heat up more and why?
a) Copper wire, higher resistance
b) Nichrome wire, higher resistance
c) Copper wire, lower resistance
d) Nichrome wire, no resistance
Ans: b) Nichrome wire, higher resistance
Q14. A lifting electromagnet stops working after being left ON for long. Why?
a) Magnetic field disappears instantly
b) Wire got heated and cell weakened
c) Iron nail lost magnetism permanently
d) Clips became non-magnetic
Ans: b) Wire got heated and cell weakened
Q15. A student connects two lemons with copper and iron electrodes to glow an LED, but it does not glow. What should be corrected first?
a) Replace lemon with apple
b) Reverse LED terminals
c) Increase lemon count
d) Use longer wires
Ans: b) Reverse LED terminals
Q16. Why does a coil without an iron core make a weaker electromagnet?
a) Iron increases resistance
b) Iron amplifies magnetic field
c) Iron blocks current leakage
d) Iron works as conductor only
Ans: b) Iron amplifies magnetic field
Q17. A compass placed near a current carrying wire shows deflection. If the current is doubled, what happens to deflection?
a) Decreases
b) Increases
c) Remains same
d) Disappears
Ans: b) Increases
Q18. Which safety device prevents overheating in household circuits?
a) Electromagnet
b) Fuse
c) Switch
d) Voltaic cell
Ans: b) Fuse
Q19. Why are rechargeable batteries preferred over single-use cells?
a) They are heavier
b) They reduce waste and cost over time
c) They last forever
d) They don’t use chemicals
Ans: b) They reduce waste and cost over time
Q20. In an experiment, a student touches a nichrome wire after current passes through it and feels it hot. What does this demonstrate?
a) Magnetic effect of current
b) Heating effect of current
c) Loss of electricity
d) Flow of resistance
Ans: b) Heating effect of current
Fill in the Blanks:
Q1. The discovery that electric current produces a magnetic field was made by __________.
a) Faraday
b) Oersted
c) Volta
d) Galvani
Ans: b) Oersted
Q2. A current-carrying coil with an iron core behaves like a strong __________.
a) Resistor
b) Electromagnet
c) Cell
d) Insulator
Ans: b) Electromagnet
Q3. The wire commonly used in heating elements is __________.
a) Copper
b) Nichrome
c) Aluminium
d) Silver
Ans: b) Nichrome
Q4. The electrolyte in a dry cell is a __________.
a) Liquid
b) Paste
c) Gas
d) Powder
Ans: b) Paste
Q5. Rechargeable batteries are widely used because they can be __________ and __________.
a) Charged, reused
b) Heated, cooled
c) Thrown, replaced
d) Shorted, repaired
Ans: a) Charged, reused
True / False:
Q1. An electromagnet has only one pole. → False
Q2. The heating effect of current depends on the resistance of the wire. → True
Q3. Dry cells can be recharged and used multiple times. → False
Q4. Earth behaves like a magnet due to movement of liquid iron in its core. → True
Q5. A fuse prevents damage from overheating in circuits. → True
Assertion–Reason:
a) Both A and R are true, and R explains A.
b) Both A and R are true, but R does not explain A.
c) A is true, R is false.
d) A is false, R is true.
Q1. Assertion (A): A compass needle deflects near a current carrying wire.
Reason (R): A current carrying wire produces a magnetic field.
Ans: a) Both A and R are true, and R explains A.
Q2. Assertion (A): Nichrome is preferred as a heating element.
Reason (R): Nichrome offers high resistance and can withstand high temperatures.
Ans: a) Both A and R are true, and R explains A.
Q3. Assertion (A): Rechargeable batteries are better than dry cells.
Reason (R): They can be reused multiple times, reducing cost and waste.
Ans: a) Both A and R are true, and R explains A.
To Learn more Click Below:
MCQs:
Chapter 1- Exploring the Investigative World of Science – CLICK HERE
Chapter 2- The Invisible Living World: Beyond Our Naked Eye – CLICK HERE
Chapter 3- Health: The Ultimate Treasure – CLICK HERE
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