A charged particle is placed at rest in a uniform magnetic field. What happens to it?
Correct answer B. It stays at rest because no magnetic force acts on it
Topic / 30 questions
Electromagnetism MCQs
Electromagnetism MCQs cover magnetic flux density and its units, magnetic flux as the dot product of B and A, and the force on and path of a charged particle moving through a magnetic field. They suit MDCAT, ECAT and FSc revision, and every question on MCQs360 shows its correct answer instantly so you can learn as you practise.
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- Dawn of Modern Physics 30
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Magnetic flux density B can be described as ____.
Correct answer C. magnetic flux per unit area perpendicular to the field
A proton moves in a circle of radius 0.20 m in a uniform magnetic field of 0.50 T. Take mₚ = 1.67 × 10⁻²⁷ kg, e = 1.6 × 10⁻¹⁹ C. What is its speed?
Correct answer A. 9.6 × 10⁶ m/s
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A magnetic flux of 3.0 × 10⁻⁴ Wb passes normally through an area of 6.0 cm². What is the magnetic flux density?
Correct answer A. 0.50 T
A long solenoid has 2000 turns per metre and carries a current of 2.0 A. Take μ₀ = 4π × 10⁻⁷ T m A⁻¹. What is the magnetic flux density inside it?
Correct answer D. 5.0 × 10⁻³ T
The magnetic flux density inside a long current-carrying solenoid depends on which pair of quantities?
Correct answer A. Number of turns per unit length and current
One tesla is the magnetic flux density in which ____.
Correct answer C. a 1 m wire carrying 1 A at right angles to the field experiences a force of 1 N
In a velocity selector, crossed electric and magnetic fields of 3.0 × 10⁴ V/m and 0.20 T act on a beam of ions. At what speed do ions pass through undeflected?
Correct answer A. 1.5 × 10⁵ m/s
At what angle to a uniform magnetic field should a current-carrying straight wire be placed to experience the greatest force?
Correct answer D. 90°
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A straight wire 0.25 m long carries a current of 4.0 A at right angles to a uniform magnetic field of 0.60 T. What force acts on the wire?
Correct answer C. 0.60 N
An alpha particle and a proton move with the same speed perpendicular to the same uniform magnetic field. Take the alpha particle’s mass as 4 times and its charge as 2 times that of the proton. What is the ratio of the radius of the alpha particle’s path to that of the proton?
Correct answer D. 2
An electron and a proton enter the same uniform magnetic field with equal velocities perpendicular to the field. Which statement is correct?
Correct answer A. They curve in opposite directions and the electron's circle is smaller
An electron moves in a circle in a uniform magnetic field of 1.0 × 10⁻³ T. Take mₑ = 9.11 × 10⁻³¹ kg, e = 1.6 × 10⁻¹⁹ C. What is its period of revolution?
Correct answer C. 3.6 × 10⁻⁸ s
For a charged particle moving in a circle in a uniform magnetic field, the time for one revolution ____.
Correct answer C. does not depend on the particle's speed
A proton travels at 1.0 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.10 T. Take mₚ = 1.67 × 10⁻²⁷ kg, e = 1.6 × 10⁻¹⁹ C. What is the radius of its circular path?
Correct answer B. 0.10 m
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A charged particle moves in a circle in a uniform magnetic field. If its speed is doubled, what happens to the radius of its path?
Correct answer B. It doubles
A charged particle enters a uniform magnetic field with its velocity at 45° to the field lines. What is the shape of its path?
Correct answer B. A helix
A charged particle enters a uniform magnetic field with its velocity perpendicular to the field. What path does it follow?
Correct answer D. A circle
An electron moves at 4.0 × 10⁵ m/s at 30° to a uniform magnetic field of 0.20 T. Take e = 1.6 × 10⁻¹⁹ C. What is the magnitude of the magnetic force on it?
Correct answer D. 6.4 × 10⁻¹⁵ N
A proton moves at 2.0 × 10⁶ m/s at right angles to a uniform magnetic field of 0.50 T. Take e = 1.6 × 10⁻¹⁹ C. What is the magnitude of the magnetic force on it?
Correct answer C. 1.6 × 10⁻¹³ N
About Electromagnetism MCQs
Questions on field quantities ask you to calculate flux density from flux and area, convert between tesla and gauss, and find flux through a surface at an angle using Φ = B·A. Questions on moving charges use F = qvB sin θ to find the magnetic force, and ask what path a particle follows when it enters a field parallel, perpendicular or at an angle to the field lines. Calculation MCQs compare the radii of the circular paths of different particles, such as protons and alpha particles, and test how the time period of revolution depends on speed.
Key facts to remember
- Magnetic force on a moving charge: F = q(v × B), with magnitude F = qvB sin θ.
- Magnetic flux Φ = B·A = BA cos θ, measured in webers (Wb).
- Magnetic flux density is measured in tesla: 1 T = 1 Wb m⁻² = 10⁴ gauss.
- A charge moving perpendicular to a uniform field follows a circle of radius r = mv/qB.
- The period of revolution T = 2πm/qB does not depend on the particle's speed or radius.
- A charge moving parallel to the field feels no force; at any other angle it follows a helical path.
Exams that include Electromagnetism MCQs
Pakistan
- MDCAT
- ECAT (UET)
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Electromagnetism MCQs
- Use r = mv/qB for ratio questions, comparing mass and charge of the particles while v and B stay the same.
- Remember the magnetic force is always perpendicular to velocity, so it changes direction but does no work.
- Convert cm² to m² (1 cm² = 10⁻⁴ m²) before calculating flux density.
- Learn the three path shapes: straight line (parallel), circle (perpendicular) and helix (at an angle).
Frequently asked questions
Which exams ask Electromagnetism MCQs?
Electromagnetism is part of the FSc physics syllabus, so its MCQs appear in MDCAT, ECAT (UET), NUMS and AKU entry tests and in FSc board papers. Students in India meet the same ideas in NEET and JEE Main, and Bangladeshi students in HSC and the medical admission test.
Why does a magnetic field do no work on a moving charge?
The magnetic force F = q(v × B) is always perpendicular to the velocity of the charge. A force at right angles to the motion changes only the direction of travel, not the speed, so the kinetic energy of the particle stays the same and no work is done.
Last reviewed October 2026