10: Electromagnetism

A region of space where magnetic forces can be felt.

A line drawn in a magnetic field so that the tangent to it at any point
shows the direction of the magnetic field at that point

* A current-carrying conductor in a magnetic field will always experience a force unless the conductor is parallel to the magnetic field.

The direction of the force is always:
• perpendicular to the current and
• perpendicular to the magnetic field

a vector whose magnitude is equal to the force experienced

by a conductor of length 1 m carrying a current of 1 A at right angles to the magnetic field

and whose direction is the direction of the force on a north pole placed at that point.

The magnetic flux density at a point is 1 tesla

if a conductor of length 1 m carrying a current of 1 A experiences a force of 1 N

when placed perpendicular to the field.

that current which, if maintained in two infinitely long parallel conductors

of negligible cross-sectional area and placed 1 metre apart in a vacuum,

would produce a force on each conductor of 2 × 10⁻⁷ newtons per metre of length.

Occurs when an emf is induced in a coil due to a changing magnetic flux

Formula
Φ = BA

(LOG TABLES)
Φ = Magnetic Flux
B = Magnetic Flux Density
A = Area

If the magnetic flux density over an area of 1 m² is 1 tesla then the flux through the area is 1 weber.

The size of emf induced is directly proportional to the rate of change of magnetic flux.

*E = – N (dΦ ÷ dt)

where N = number of turns

The direction of an induced emf is such as to oppose the change causing it.

A device that converts mechanical energy to electrical energy

Occurs in two adjacent coils when the magnetic field in one coil changes and an emf is induced in the other

Occurs when a changing magnetic field in a coil induces an emf in the coil itself

A device which changes the size of an alternating voltage