electromagnetism, generators and transformers

Question 1

what is a magnetic field?

Answer 1

path taken by a freely moving North pole

Question 2

what are magnetic field lines?

Answer 2

fill the space around a magnet where the magnetic forces work and where they attract or repel magnetic material.

Question 3

how do you detect magnetic field lines?

Answer 3

iron fillings

Question 4

what are the rules of a magnetic field line drawing?

Answer 4

arrows that come from north to south

field lines are more concentrated at the poles

Question 5

where is the magnetic field the strongest?

Answer 5

at the poles where the field lines are more concentrated

Question 6

how do you find the direction and shape of the magnetic field?

Answer 6

by plotting compasses

Question 7

what is Flemming’s left hand rule?

Answer 7

helps remember the direction of motion in an electric motor
First finger - direction of the magnetic Field (N - S)
seCond finger - direction of the Current (+ - -)
thuMb - direction of Movement

Question 8

what is the motor effect?

Answer 8

when a current-carrying wire or coil can exert a force on a permanent magnet

Question 9

what happens when a current runs through the coil in an electric motor?

Answer 9

the coil experiences a force and moves

Question 10

why does the direction of current have to be reversed every half turn in a moving electric motor?

Answer 10

because if you do not the coil comes to a halt and stops turning

Question 11

how do you switch the direction of current every half turn?

Answer 11

by a split ring or commutator

Question 12

how do you increase the size of a force?

Answer 12

increase stength of magnetic field

increase current

Question 13

how do you increase the turning effect of an electric motor?

Answer 13

increase current
increase turns on the coil
increase strength of magnetic field
increase area of the coil
use an iron core

Question 14

how is an induced voltage produced?

Answer 14

when a magnet moved into coil of wire

Question 15

how id the direction of the induced voltage changed?

Answer 15

when the magnet is moved out of the coil again

Question 16

is there an induced voltage if there is no current?

Answer 16

no

Question 17

how do you increase an induced voltage?

Answer 17

move the magnet faster
add more turns to the coil
increase strength of the magnet

Question 18

what happens if wire is moved down?

Answer 18

galvanometer goes to the left

Question 19

what happens if wire is moved up?

Answer 19

galvanometer goes to the right

Question 20

what happens if wire is moved sideways?

Answer 20

stays at 0

Question 21

how do you find current direction in electromagnetic induction?

Answer 21

right hand rule
first finger - field lines
second finger - current
thumb - movement

Question 22

how do you increase the size of an induced current or voltage?

Answer 22

increase speed of movement
increase strength of magnetic field
increase number of turns on the coil
increase area of coil

Question 23

why is the current and voltage produced maximum when coil turns?

Answer 23

more field lines are cut per second

Question 24

what is the national grid?

Answer 24

a network of power stations, transformers and cables which distributes electricity across the country

Question 25

what does a step up transformer have more of than a step down transformer? what does this do?

Answer 25

more turns of wire on the coil

creates a larger induced voltage in the secondary coil

Question 26

how does a transformer work?

Answer 26

alternating current/ voltage in the primary coil creates an alternating magnetic field through the primary coil. The iron core traps the magnetic field and links it to the secondary coil. The changing magnetic field through the secondary coil induces an alternating current/ voltage

Question 27

why does an alternating voltage on the input have to be used?

Answer 27

to create an alternating magnetic field