JEE · Physics · Magnetism & Electromagnetic Induction doubts
14 doubts found
What does “Magnetic force on a moving charge” actually mean in Magnetism & Electromagnetic Induction, and why does it matter for JEE?
F = qvB·sinθ, always perpendicular to the velocity, so it changes direction but not speed.
I keep getting “Magnetic force on a moving charge” questions wrong in Magnetism & Electromagnetic Induction. What's the trap?
thinking the magnetic force can speed a charge up.
What does “Faraday's law of induction” actually mean in Magnetism & Electromagnetic Induction, and why does it matter for JEE?
a changing magnetic flux induces an EMF, EMF = −dΦ/dt.
I keep getting “Faraday's law of induction” questions wrong in Magnetism & Electromagnetic Induction. What's the trap?
expecting a steady (unchanging) magnetic field to induce an EMF.
What does “Lenz's law” actually mean in Magnetism & Electromagnetic Induction, and why does it matter for JEE?
the induced current always opposes the change that produced it, ensuring energy conservation.
I keep getting “Lenz's law” questions wrong in Magnetism & Electromagnetic Induction. What's the trap?
getting the direction of induced current backwards.
What does “Magnetic flux” actually mean in Magnetism & Electromagnetic Induction, and why does it matter for JEE?
Φ = B·A·cosθ — the amount of field passing through a loop.
I keep getting “Magnetic flux” questions wrong in Magnetism & Electromagnetic Induction. What's the trap?
ignoring the angle between the field and the loop's normal.
What is the difference between electric force and magnetic force (on a charge)?
The electric force acts along the field and can do work; the magnetic force acts perpendicular to velocity and does no work.
What is the difference between Faraday's law and Lenz's law?
Faraday's law gives the SIZE of the induced EMF; Lenz's law gives its DIRECTION (opposing the change).
What is the difference between AC and DC?
Alternating current periodically reverses direction (mains supply); direct current flows one way (batteries).
When do I use F = qvB sinθ in Magnetism & Electromagnetic Induction, and what does it mean?
force on a charge moving through a magnetic field.
When do I use F = BIL sinθ in Magnetism & Electromagnetic Induction, and what does it mean?
force on a current-carrying wire in a field.
When do I use EMF = −dΦ/dt in Magnetism & Electromagnetic Induction, and what does it mean?
Faraday's law of electromagnetic induction.