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Magnetic Force Questions Right-Hand Rule Real-Life Magnetism
Magnetic force on charges is one of the most scoring and concept-based topics in Class 12 Physics. If you understand this chapter properly, you can solve numericals quickly and avoid common mistakes in exams.
In this blog, we’ll go through top 20 important questions, along with clear explanations, formulas, and exam tips-just like a classroom session.
When a charged particle moves in a magnetic field, it experiences a force:
F = qvB sinθ
| Concept | Meaning | Key Point |
|---|---|---|
| Magnetic Force | Force on moving charge | Only acts on moving charges |
| Direction | Right-Hand Rule | Perpendicular to v and B |
| Maximum Force | θ = 90° | sin90° = 1 |
| Zero Force | θ = 0° | No force |
Q1. What happens when a stationary charge is placed in a magnetic field?
No force acts because velocity is zero.
Q2. When is magnetic force maximum?
When angle between velocity and field is 90°.
Q3. When is magnetic force zero?
When motion is parallel or anti-parallel.
Q4. Does magnetic force change speed?
No, it only changes direction.
Q5. Why is magnetic force perpendicular?
Because it is based on cross product.
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| Situation | Formula | Result |
|---|---|---|
| General | F = qvB sinθ | Depends on angle |
| θ = 90° | F = qvB | Maximum |
| θ = 0° | F = 0 | No force |
Q6. Path in uniform magnetic field?
Circular motion.
Q7. Radius formula?
r = mv/qB
Q8. Time period?
T = 2πm/qB
Q9. Frequency?
f = qB/2πm
Q10. Velocity at angle?
Helical motion.
| Condition | Motion | Reason |
|---|---|---|
| v ⟂ B | Circular | Centripetal force |
| v ∥ B | Straight | No force |
| Angle | Helical | Combined motion |
Q11. Direction of force?
se Right-Hand Rule.
Q12. Negative charge?
Direction reverses.
Q13. Lorentz Force?
F = q(E + v × B)
Q14. Cyclotron motion?
Circular motion in magnetic field.
Q15. Uniform magnetic field?
No energy loss.
| Concept | Real-Life Analogy |
|---|---|
| Circular motion | Stone on string |
| Magnetic force | Invisible steering |
| Helical motion | Spiral staircase |
Q16. Force calculation
F = 2 × 3 × 4 = 24 N
Q17. Radius
r = 4 m
Q18. Time period
Use T = 2πm/qB
Q19. Velocity selector
v = E/B
Q20. Energy change
No change in kinetic energy.
Explore more questions: Click here
Practice quizzes: Start now
| Mistake | Correct Concept |
|---|---|
| Ignoring angle | Always use sinθ |
| Wrong direction | Use right-hand rule |
| Speed changes | Only direction changes |
Download worksheets for more practice: Click here
If you want to practice this topic, you can take a quiz in Curious Corner for better practice.
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