IIT JEE Physics Magnetism and Electromagnetic Induction practice paper with 30 MCQs, answers, explanations and instant score.
30 Questions | 4 Marks Each | No Negative Marking
Magnetism & Electromagnetic Induction – IIT JEE Notes (Set 3)
Magnetic Field Basics
Definition
A magnetic field is the region around a magnet or current-carrying conductor where magnetic force can be experienced by moving charges or magnetic materials.
SI Unit
The SI unit of magnetic field is Tesla (T). It is a vector quantity and has both magnitude and direction.
Magnetic Force on Moving Charge
Lorentz Force
F = qvB sinθ
The magnetic force depends on charge, velocity, magnetic field, and angle between velocity and field.
Important Insight
If velocity is parallel to magnetic field, force is zero. If perpendicular, force is maximum.
Force on Current Carrying Conductor
Formula
F = BIL sinθ
Where B is magnetic field, I is current, and L is length of conductor.
Direction Rule
Fleming’s Left Hand Rule gives the direction of force acting on the conductor.
Magnetic Field Due to Current
Straight Wire
B ∝ I / r
Magnetic field increases with current and decreases with distance from wire.
Circular Loop
B = μ₀I / 2R
Magnetic field is strongest at the center of the loop.
Magnetic Flux
Definition
Φ = B × A × cosθ
Magnetic flux represents the number of magnetic field lines passing through a surface.
Unit
The SI unit of magnetic flux is Weber (Wb).
Electromagnetic Induction (EMI)
Faraday’s Law
Induced emf is proportional to rate of change of magnetic flux.
ε = – dΦ/dt
Key Concept
Faster change in flux produces larger induced emf. This is widely used in generators.
Lenz’s Law
Statement
The direction of induced current opposes the cause producing it.
Important Insight
Lenz’s law is based on conservation of energy and prevents violation of energy principles.
Induced Current
Conditions
Induced current is produced when there is a change in magnetic flux through a circuit.
Methods to Change Flux
Change magnetic field, change area, or change orientation of the loop.
Self Inductance
Definition
Self inductance is the property of a coil to oppose change in current flowing through it.
Formula
ε = -L (dI/dt)
Mutual Inductance
Definition
It is the property by which a change in current in one coil induces emf in another coil.
Application
Used in transformers and wireless energy transfer systems.
Alternating Current Basics
AC Current
Current that changes direction periodically is called alternating current.
Frequency
In India, AC frequency is 50 Hz.
Key Exam Concepts
Conceptual Traps
Magnetic force does no work as it is perpendicular to velocity. Electric field can do work but magnetic field cannot.
JEE Strategy
Focus on right-hand rules, formulas, and conceptual understanding. Practice numerical problems involving magnetic force and induction carefully.