Physics - Magnetism

Magnetic field

Any region of space where magnetic forces can be felt. The direction of the magnetic field at a point is the direction of the force of a North Pole if it were placed at that point.

Right hand grip rule

Imagine to grip a wire with RIGHT hand, with the thumb pointing in the direction of the current. The fingers give the direction of the magnetic field

Fleming's left hand rule

states that if the thumb, first finger and second finger of the left hand are held at right angles, with the first finger pointed in the direction of the magnetic field and the second finger pointing in the direction of the current, the thumb points in the direction of the force. Remember FBI: F(force) - Thumb; B(magnetic field) - index; I(current) - middle finger

Magnetic flux density

At a point in a magnetic field is a vector whose magnitude is equal to the force that a conductor of 1m carrying 1A at RIGHT ANGLES to the field at that point and whose direction is the direction of the force on a north pole placed at that point would be experiencing. Unit= Tesla (T)

Electromagnetic induction

Whenever the magnetic field passing through a coil changes, an emf appears in the coil

Faraday's Law

The size of induced EMF is directly proportional to the rate of change of the flux = change in flux/time taken

Lenz's law

Direction of induced EMF is always opposite to the direction of the charge producing it

Electric generators

devices that convert mechanical energy into electrical energy

mutual induction

The cangi g magnetic field in one coil causes an induced EMF to appear in a nearby coil

self induction

The current passing trough a coil changes, the magnetic field surrounding it changes. This changing magnetic field induces an EMF in the coil that opposes the changing current

Transformer

A device that increases or decreases the voltage of alternating current (based on principle of mutual induction)