Kerala SSLC · Physics · Class 10
Electromagnetic Induction: Important Questions with Answers
These are 10 important multiple-choice questions from the Kerala SSLC Physics chapter “Electromagnetic Induction” (Kerala SCERT syllabus). Each one shows the correct answer and a short explanation of why it is right. Try answering before you read the answer. ExamSummary has 10 practice questions on this chapter in total.
Q1.Under which condition is an electromotive force (emf) induced in a closed coil?
- A)When the coil is placed near a strong magnet without moving.
- B)When there is relative motion between the magnet and the coil.
- C)When the coil is rotated slowly in a uniform magnetic field.
- D)When the magnetic field lines are parallel to the plane of the coil.
Answer: B) When there is relative motion between the magnet and the coil.
Electromagnetic induction occurs only when there is a change in the magnetic flux linked with the coil. This change is primarily achieved through relative motion between the magnet and the coil.
Q2.Which rule is used to determine the direction of the induced current in a conductor moving in a magnetic field?
- A)Fleming’s Left-Hand Rule
- B)Maxwell’s Corkscrew Rule
- C)Fleming’s Right-Hand Rule
- D)Right-Hand Thumb Rule
Answer: C) Fleming’s Right-Hand Rule
Fleming’s Right-Hand Rule is specifically used for induced current in generators where motion creates electricity. The thumb, forefinger, and middle finger represent motion, field, and current respectively.
Q3.If a bar magnet is held stationary inside a coil connected to a galvanometer, what will happen?
- A)The galvanometer shows a constant deflection.
- B)The galvanometer shows momentary deflection.
- C)There is no deflection in the galvanometer.
- D)The galvanometer needle oscillates continuously.
Answer: C) There is no deflection in the galvanometer.
Induced current requires a change in magnetic flux over time. Since the magnet is stationary, the flux remains constant, so no emf is induced and the needle stays still.
Q4.An electric generator converts which form of energy into electrical energy?
- A)Chemical energy to electrical energy
- B)Mechanical energy to electrical energy
- C)Electrical energy to mechanical energy
- D)Thermal energy to electrical energy
Answer: B) Mechanical energy to electrical energy
Generators operate on the principle of electromagnetic induction to produce electricity. They require mechanical input, such as rotating a coil, to generate electrical output.
Q5.In an AC generator, what component allows the current to flow out of the rotating coil to the external circuit?
- A)Commutator
- B)Carbon Brushes and Slip Rings
- C)Split Rings
- D)Solenoid
Answer: B) Carbon Brushes and Slip Rings
Slip rings maintain continuous contact with the carbon brushes to transfer alternating current from the rotating coil. Commutators are typically used in DC generators to reverse the current direction.
Q6.The commercial frequency of alternating current supplied in Kerala is:
- A)60 Hz
- B)50 Hz
- C)100 Hz
- D)220 Hz
Answer: B) 50 Hz
In India, including Kerala, the standard frequency for household AC supply is 50 Hertz. This means the current changes direction 50 times per second.
Q7.According to Lenz’s Law, the direction of the induced current is such that it:
- A)Supports the change in magnetic flux.
- B)Opposes the change in magnetic flux that produced it.
- C)Increases the speed of the magnet.
- D)Remains independent of the magnetic field.
Answer: B) Opposes the change in magnetic flux that produced it.
Lenz’s Law states that the induced current flows in a direction to oppose the cause producing it. This is a fundamental consequence of the conservation of energy.
Q8.Which factor does NOT affect the magnitude of the induced emf in a coil?
- A)Strength of the magnetic field
- B)Number of turns in the coil
- C)Speed of relative motion
- D)Color of the wire used
Answer: D) Color of the wire used
The induced emf depends on magnetic field strength, number of turns, and rate of change of flux. The physical color of the wire has no effect on electromagnetic induction principles.
Q9.What is the primary function of a transformer in an electrical circuit?
- A)To convert AC to DC
- B)To step up or step down AC voltage
- C)To store electrical energy
- D)To measure electric current
Answer: B) To step up or step down AC voltage
Transformers work on mutual induction to increase (step-up) or decrease (step-down) alternating voltage levels. They cannot be used with direct current (DC).
Q10.When the north pole of a magnet approaches a coil, the face of the coil nearest to the magnet becomes:
- A)South Pole
- B)North Pole
- C)Neutral Pole
- D)East Pole
Answer: B) North Pole
To oppose the approaching north pole, the coil induces a north pole on its facing side to create repulsion. This follows Lenz’s Law regarding opposing the change in flux.