Electricity Magnetic and Heating Effects Class 8 MCQ
hardElectricity Magnetic and Heating Effects Class 8 MCQ
Electricity Magnetic and Heating Effects Class 8 MCQ
Question 1.
What happens to a nichrome wire when an electric current flows through it?
(a) It becomes cold.
(b) It becomes warm.
(c) It becomes a magnet.
(d) It breaks.
Answer:
(b) It becomes warm.
Question 2.
Which of the following devices works on the magnetic effect of electric current?
(a) Electric heater
(b) Voltaic cell
(c) Electric iron
(d) Electromagnet
Answer:
(d) Electromagnet
Question 3.
Why is nichrome wire commonly used in electrical heating devices?
(a) It is a good conductor of electricity.
(b) It generates more heat for a given current.
(c) It is cheaper than copper.
(d) It is an insulator of electricity.
Answer:
(b) It generates more heat for a given current.
Question 4.
When a current-carrying coil is placed near a compass, what happens to the compass needle?
(a) It remains unaffected.
(b) It deflects.
(c) It breaks.
(d) It turns into a magnet.
Answer:
(b) It deflects.
Question 5.
What is the primary reason electric heating devices are considered more convenient than traditional heating methods?
(a) They are more expensive.
(b) They require no fuel.
(c) They generate heat instantly and can be controlled easily.
(d) They are less effective.
Answer:
(c) They generate heat instantly and can be controlled easily.
Question 6.
If the battery terminals in a circuit are reversed, what will happen to the deflection of the compass needle?
(a) It will not change.
(b) It will deflect in the opposite direction.
(c) It will break.
(d) It will stop working.
Answer:
(b) It will deflect in the opposite direction.
Question 7.
In a lifting electromagnet, why does the iron nail stop picking up paper clips when the circuit is opened?
(a) The wire becomes cold.
(b) The current stops flowing, and the magnetic field disappears.
(c) The iron nail becomes too heavy.
(d) The paper clips are removed.
Answer:
(b) The current stops flowing, and the magnetic field disappears.
Question 8.
Which of the following statements is true regarding a Voltaic cell?
(a) It generates electric current through mechanical energy.
(b) It generates electric current through chemical reactions.
(c) It requires an external power source to operate.
(d) It is only used in electric heaters.
Answer:
(b) It generates electric current through chemical reactions.
Question 9.
What is the heating effect of electric current?
(a) It causes the wire to become a magnet.
(b) It generates light.
(c) It causes the conductor to heat up due to resistance.
(d) It makes the circuit break.
Answer:
(c) It causes the conductor to heat up due to resistance.
Question 10.
Which material is best suited for making electric heating elements?
(a) Copper
(b) Aluminium
(c) Nichrome
(d) Iron
Answer:
(c) Nichrome
Case Study
I. The Magnetic Effect of Electric Current
When an electric current flows through a conductor, it generates a magnetic field around it, a phenomenon known as the magnetic effect of electric current. This principle is fundamental in creating electromagnets, which are coils of wire that behave like magnets when current passes through them. For instance, wrapping a wire around an iron nail and connecting it to a battery can create a strong electromagnet capable of lifting small metal objects. This application is widely utilised in industries for moving heavy materials efficiently.
Question 1.
What happens when an electric current flows through a conductor?
(a) It produces heat only.
(b) It generates a magnetic field around it.
(c) It creates sound waves.
(d) It causes the conductor to glow.
Answer:
(b) It generates a magnetic field around it.
Question 2.
Which of the following is a practical application of electromagnets?
(a) They are used to generate electricity in power plants.
(b) They are used in electric bells and motors.
(c) They are used to measure temperature.
(d) They are used to purify water.
Answer:
(b) They are used in electric bells and motors.
Question 3.
The phenomenon where electric current generates a magnetic field around a conductor is known as the .............. of electric current.
Answer:
magnetic effect
Question 4.
When an electromagnet is created by wrapping a wire around an iron nail and connecting it to a battery, it can lift ........... objects.
Answer:
small metal
Question 5.
An electromagnet can only dift objects when the electric current is flowing through the wire. (True/False)
Answer:
True
II. Heating Effects in Conductors
The flow of electric current through a conductor also produces heat, known as the heating effect of electric current. This effect is particularly evident when using nichrome wire, which is often employed in heating elements due to its high resistance. When current flows through nichrome wire, it heats up significantly, demonstrating that thicker wires can carry more current with less heating compared to thinner wires. This principle is crucial in designing electrical appliances that require heat, such as toasters and electric heaters.
Question 1.
What is the primary reason nichrome wire is used in heating elements?
(a) It is a good conductor of electricity.
(b) It generates more heat for a given current due to its high resistance.
(c) It is cheaper than copper.
(d) It is an insulator of electricity.
Answer:
(b) It generates more heat for a given current due to its high resistance.
Question 2.
Which of the following statements is true regarding the heating effect of electric current?
(a) Thinner wires can carry more current with less heating compared to thicker wires.
(b) The heating effect is only observed in copper wires.
(c) The amount of heat generated in a wire depends on the material, thickness, and duration of current flow.
(d) Electric current does not produce any heat in conductors.
Answer:
(c) The amount of heat generated in a wire depends on the material, thickness, and duration of current flow.
Question 3.
The phenomenon where electric current flowing through a conductor produces heat is known as the ............ effect of electric current.
Answer:
heating
Question 4.
Nichrome wire is commonly used in electric heating devices because it has a ............ resistance compared to other conductors like copper.
Answer:
high
Question 5.
Thicker wires always generate more heat than thinner wires when the same amount of current flows through them. (True/False)
Answer:
False