Free Electromagnetism MCQs with Answers
1,176 Electromagnetism MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Magnetic flux density and magnetic flux describe the strength of a magnetic field and the field passing through a surface. A charged particle moving through a magnetic field experiences a force perpendicular to its velocity and may follow circular or helical motion, depending on the angle between velocity and field.
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- A. air
- B. steel
- C. Cu-Ni alloy
- D. soft iron
Explanation: Soft iron is suitable for an electromagnet because it has high magnetic permeability and loses most of its magnetism when the current is…
Correct answer: soft iron- A. repel each other
- B. attract each other
- C. have no effect upon each other
- D. they cancel out their individual magnetic fields
Explanation: Parallel currents in the same direction attract, while parallel currents in opposite directions repel because of the magnetic force…
Correct answer: repel each other- A. 1A
- B. 10A
- C. 100A
- D. 1000A
Explanation: For a wire perpendicular to the field, F = BIL. Thus I = F/(BL) = 5 N / [(0.5 T)(0.10 m)] = 5 N / 0.05 T m = 100 A, since 1 T m A = 1 N.
Correct answer: 100A- A. magnetic flux
- B. magnetic field intensity
- C. magnetic induction
- D. self inductance
Explanation: From F = qvB for perpendicular motion, B = F/(qv). For a unit positive charge and unit velocity, B equals the magnetic force numerically…
Correct answer: magnetic induction- A. Demagnetization
- B. Breakage
- C. Extension
- D. Surface cracking
Explanation: Coercive force is the reverse magnetic field required to reduce the magnetisation of a magnet to zero, so it opposes demagnetisation.
Correct answer: Demagnetization- A. Semi-conductor becomes conductors
- B. Ferromagnetic becomes paramagnetic
- C. Paramagnetic becomes diamagnetic
- D. Metals become super conductor
Explanation: At the Curie temperature, thermal agitation destroys the long-range alignment of magnetic domains, changing a ferromagnetic material into…
Correct answer: Ferromagnetic becomes paramagnetic- A. Hysteresis curve
- B. Hysteresis loop area
- C. Hysteresis loop
- D. Straight line
Explanation: The area enclosed by a hysteresis loop represents the energy lost per unit volume in one complete magnetisation cycle, so it measures the…
Correct answer: Hysteresis loop area- A. Squids
- B. Magnetic resonance imaging (MRI)
- C. Magnetometer
- D. Oscilloscope
Explanation: SQUIDs, or superconducting quantum interference devices, detect extremely small changes in magnetic flux and are therefore used for very…
Correct answer: Squids- A. High voltage A.C
- B. Low voltage A.C
- C. Alternating current at its peak value
- D. D.C current at peak value
Explanation: For an alternating magnetizing current, the magnetic field reaches its greatest value when the current is at its peak, allowing a…
Correct answer: Alternating current at its peak value- A. magnetic flux = flux density / area
- B. magnetic flux = flux density x area
- C. flux density = magnetic flux area
- D. flux density = magnetic flux x area
Explanation: Magnetic flux through an area is Φ = BA when the field is perpendicular to the area, where Φ is in Wb, B is in Wb m^-2, and A is in m^2.
Correct answer: magnetic flux = flux density x area- A. 2πm/qB
- B. 2πm/qBr
- C. qrB/m
- D. 2πmq/rB
- E. 2mq/rB
Explanation: The correct answer is Option A: 2πm/qB. When a charged particle moves in a magnetic field, the magnetic force acts as the centripetal…
Correct answer: 2πm/qB- A. 9.1 x 10^-3 m
- B. 9.1 x 10^-2 m
- C. 1.9 x 10^-3 m
- D. 1.9 x 10^-2 m
- E. 9.1 x 10^-1 m
Explanation: The radius of the orbit of an electron moving in a uniform magnetic field is given by the equation: r = mv/eB Where r is the radius of the…
Correct answer: 9.1 x 10^-3 m- A. 0.002 T
- B. 2.5 x 10^-6 T
- C. 0.005 T
- D. 4 x 10^-6 T
Explanation: The magnetic field at ground due to a current-carrying wire is given by the formula:B = μ₀I/(2πr)where μ₀ is the permeability of free…
Correct answer: 2.5 x 10^-6 T- A. F = Qb
- B. F = qB2
- C. F = qB/v
- D. F = qvB
Explanation: This is a standard answer. A charged particle moving perpendicular to a constant magnetic field experiences a magnetic force F, which…
Correct answer: F = qvB- A. Reflecting force
- B. Restoring force
- C. Deflecting force
- D. Gravitational force
Explanation: Magnetic force is simply a deflecting force. It will change the direction of charge particle moving in magnetic field.
Correct answer: Deflecting force- A. Charged positive particles
- B. Charged negative particles
- C. Neutral particles
- D. All of these
Explanation: Correct option is C. Magnetic fields will not be produced in case of neutral particles.
Correct answer: Neutral particles- A. Moving charge
- B. Charge in magnetic flux
- C. Current flowing in conductor
- D. Stationary charge
Explanation: A magnetic field does not affect a stationary charge because it has no velocity.
Correct answer: Stationary charge- A. Parabolic
- B. Circular
- C. Parallel to v
- D. Parallel to B
Explanation: Option A) Parabolic is not correct because a parabolic path would require an additional force acting on the charged particle, which is not…
Correct answer: Circular- A. Decreases
- B. Increases then decreases
- C. Becomes zero
- D. Remains constant
Explanation: Option A : When a charged particle enters a magnetic field, its K.E. not decreases.
Correct answer: Remains constant- A. It will also double
- B. It will be halved
- C. It will increase four times
- D. Remain unchanged
Explanation: It will remain unchanged. As the frequency of revolution in a cyclotron υC=Bq2πm is independent of r.
Correct answer: Remain unchanged