# 5.1.3 ELECTROMAGNETISM

HideShow resource information
What is magnetic flux?
magnetic flux density x cross sectional area perp to magnetic field
1 of 14
What is magnetic flux measured in? define it
WEBBER/ magnetic flux density 1T passing normally through an area of 1m2
2 of 14
What is magnetic flux linkage? what is it measured in?
product of magnetic flux and n of turns of a conductor/ webber
3 of 14
induced emf is prop ro the rate of change of magnetic flux linkage/ emf = NBA/t
4 of 14
How else can emf be found?
5 of 14
What is Lenz law? what is it a product of?
the direction of induced emf or current is such that to oppose the change producing it (-NBA/t)
6 of 14
Explain Lenz's Law
work it does to push the magnet into the coil against the repulsive force/ the energy resulting from the work is transferred into electric energy of the current
7 of 14
Describe the function of an AC generator
convert kinetic energy into electrical energy/ rotation of coil induces emf across ends of the coil/ slip ring and brushes allow circuit to remain complete - ac current
8 of 14
what is the maximum induced emf depend on?
directly prop to / frequency of rotation/ B/ N/ A
9 of 14
describe the structure of transformers
two coils of insulted wire wound around laminated soft iron core
10 of 14
Describe how a transformer works
alternating current of primary coil produces a changing magnetic field/ changing field links to secondary/ change in the rate of magnetic flux linkage/ induces emf in secondary
11 of 14
Describe a step up transformer
Vs is bigger than Vp/ Ns is bigger than Np/ low to high voltage
12 of 14
Describe a step down transformer
Vp bigger than Vs/ more turns on primary/ high to low volatge
13 of 14
Why are transformers used?
electricity from power station sent around on grid at lowest possible current so less is los to resistance/ Power = IV low current high voltage
14 of 14

## Other cards in this set

### Card 2

#### Front

What is magnetic flux measured in? define it

#### Back

WEBBER/ magnetic flux density 1T passing normally through an area of 1m2

### Card 3

#### Front

What is magnetic flux linkage? what is it measured in?

### Card 5

#### Front

How else can emf be found?