Magnetic

Magnetic Flux Density, B

The force acting per unit current on a wire of unit length, placed at right angles to a uniform magnetic field

F=BILsinx or (moving charge) F=Bqvsinx

Magnetic Flux, T

Product of magnetic flux density, B and cross-sectional area perpendicular to direction of B

at 90• → max

BAcosx

Magnetic Flux Linkage of a coil w N turns

Product of Magnetic Flux passing through a coil and the number of turns, N of a coil

NBAcosx

Faraday

The magnitude of induced emf in a coil is equal to rate of change of magnetic flux linkage of the coil

emf = -d(magnetic flux linkage)/dt

= - d(NBAcosx)/dt

Lenzs Law

Direction of induced emf opposed the change which causes it

Induced EMF of straight conductor

BLvsinx

Explanation

By Faradays, changing magnetic flux linkage produces an induced EMF, hence induced current

By Lenzs law, force due to induced current opposes motion

Rotating Disc EMF

-B pi r² f

path of angle 0<x<90

Helical path