Physics Grade 12 Unit 4 Electromagnetism MCQs with explanation
PART 2
6. You are looking directly into one end of a long solenoid. The magnetic field at its center points at you. What is the direction of the current in the solenoid, as viewed by you?
A. clockwise
B. counterclockwise
C. directly toward you
D. directly away from you
Answer B. counterclockwise.
Explanation:
• To determine the direction of the current in a solenoid, you can use the right-hand rule.
• If you curl the fingers of your right hand in the direction of the current, your thumb will
point in the direction of the magnetic field inside the solenoid.
7. The number of turns in a solenoid is doubled, and its length is halved. How does its magnetic field change?
A. It triples.
B. It is halved.
C. It quadruples.
D. It doubles.
Answer C
𝐁 = 𝝁𝒐𝐈𝑵/𝒍
8. According to Faraday’s law of electromagnetic induction
A. Electric field is produced by time varying magnetic flux
B. Magnetic field is produced by time varying electric flux.
C. Magnetic field is associated with a moving charge.
D. None of the above
Answer A.
Explanation: Faraday’s Law of Electromagnetic Induction states that a time-varying magnetic flux through a loop of wire induces an electromotive force (emf) and, consequently, an electric field in the loop.
• This induced electric field is non-conservative and is created by the changing magnetic field.
9. The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a short galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was
A. Moving towards the solenoid
B. Moving into the solenoid
C. At rest inside the solenoid
D. Moving out of the solenoid
Answer D.
Explanation:
• According to Faraday's Law of Induction, an electromotive force (EMF) is induced in
the solenoid when the magnetic flux through the solenoid changes.
• The maximum deflection of the galvanometer occurs when there is a rapid change in the
magnetic flux.
• The flux through the solenoid changes most rapidly when the magnet is moving out of the
solenoid because this movement causes the magnetic field to change quickly, inducing the maximum current in the solenoid
10. A bar magnet is divided in two pieces. Which of the following statements is true about the force between the broken pieces if they face each other with a small separation?
A. There is an electric repulsive force between the broken pieces.
B. There is an electric attractive force between the broken pieces.
C. There is a magnetic repulsive force between the broken pieces.
D. There is a magnetic attractive force between the broken pieces.
Answer D.
Explanation:
• When a bar magnet is broken into two pieces, each piece becomes a smaller magnet with its own north and south poles.
• These smaller magnets will attract each other because the opposite poles (north and south) of the broken pieces will face each other, creating a magnetic attractive force.
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PART 2
6. You are looking directly into one end of a long solenoid. The magnetic field at its center points at you. What is the direction of the current in the solenoid, as viewed by you?
A. clockwise
B. counterclockwise
C. directly toward you
D. directly away from you
Answer B. counterclockwise.
Explanation:
• To determine the direction of the current in a solenoid, you can use the right-hand rule.
• If you curl the fingers of your right hand in the direction of the current, your thumb will
point in the direction of the magnetic field inside the solenoid.
7. The number of turns in a solenoid is doubled, and its length is halved. How does its magnetic field change?
A. It triples.
B. It is halved.
C. It quadruples.
D. It doubles.
Answer C
𝐁 = 𝝁𝒐𝐈𝑵/𝒍
8. According to Faraday’s law of electromagnetic induction
A. Electric field is produced by time varying magnetic flux
B. Magnetic field is produced by time varying electric flux.
C. Magnetic field is associated with a moving charge.
D. None of the above
Answer A.
Explanation: Faraday’s Law of Electromagnetic Induction states that a time-varying magnetic flux through a loop of wire induces an electromotive force (emf) and, consequently, an electric field in the loop.
• This induced electric field is non-conservative and is created by the changing magnetic field.
9. The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a short galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was
A. Moving towards the solenoid
B. Moving into the solenoid
C. At rest inside the solenoid
D. Moving out of the solenoid
Answer D.
Explanation:
• According to Faraday's Law of Induction, an electromotive force (EMF) is induced in
the solenoid when the magnetic flux through the solenoid changes.
• The maximum deflection of the galvanometer occurs when there is a rapid change in the
magnetic flux.
• The flux through the solenoid changes most rapidly when the magnet is moving out of the
solenoid because this movement causes the magnetic field to change quickly, inducing the maximum current in the solenoid
10. A bar magnet is divided in two pieces. Which of the following statements is true about the force between the broken pieces if they face each other with a small separation?
A. There is an electric repulsive force between the broken pieces.
B. There is an electric attractive force between the broken pieces.
C. There is a magnetic repulsive force between the broken pieces.
D. There is a magnetic attractive force between the broken pieces.
Answer D.
Explanation:
• When a bar magnet is broken into two pieces, each piece becomes a smaller magnet with its own north and south poles.
• These smaller magnets will attract each other because the opposite poles (north and south) of the broken pieces will face each other, creating a magnetic attractive force.
Join
https://t.me/QuickLearngEthiopia
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