electromagnetism

Question 1

what can an electric current in a conductor produce

Answer 1

a magnetic field around it

Question 2

if the electric current is larger what is the magnetic field

Answer 2

stronger

Question 3

what does the direction of the magnetic field depend on

Answer 3

the direction of the current

Question 4

the magnetic field inside a current carrying solenoid is..

Answer 4

strong and uniform

Question 5

what does it mean if a magnetic material is ‘soft’

Answer 5

it looses its induced magnetism quickly

Question 6

what does it mean if a magnetic material is ‘hard’

Answer 6

its induced magnetism is permanent

Question 7

what is an example of a magnetically hard and soft material

Answer 7

hard-steel
soft-iron

Question 8

how is a current carrying wire formed

Answer 8

when two magnetic fields affect each other it causes a force on the wire causing the wire to move- also known as motor effect

Question 9

for a wire to experience full force what angle does the wire have to be to the magnetic field

Answer 9

90 degrees

Question 10

what 4 things do the magnitude of the force in the motor effect increase with

Answer 10

-strength of magnetic field
-amount of current flowing through the conductor
-a soft iron core
-more turns on the coil

Question 11

what does a split ring commutator do

Answer 11

it swaps the contacts every half turn to keep the motor rotating in the same direction

Question 12

what does reversing the current or magnetic field also do

Answer 12

reverse direction of the force

Question 15

how does a loudspeaker work

Answer 15

1) electrical signals from an amplifier are fed from a coil of wire in the speaker which is wrapped around the base of a cone
2) coil is surrounded by a permanent magnet so the A.C signals cause a force on the coil so it moves back and forth
3)this causes the cone to vibrate and make sounds

Question 16

what is electromagnet induction

Answer 16

the creation of voltage in a wire which is experiencing a change in magnetic field

Question 17

what does electromagnetic induction use to generate electricity

Answer 17

energy from kinetic stores called the dynamo effect

Question 18

what do generators do

Answer 18

rotate a coil in a magnetic field

Question 19

in a.c generators what happens when the coil spins

Answer 19

a current is induced in the coil and the current changes direction every half turn

Question 20

what do A.C generators have instead of split ring commutators

Answer 20

slip rings and brushes

Question 21

where are A.C generators commonly used in

Answer 21

power stations

Question 22

what do transformers do

Answer 22

change the size of the voltage of an alternating current

Question 23

what do all transformers have

Answer 23

two coils, the primary and secondary joined with an iron core

Question 24

what does a step up transformer do

Answer 24

increase the voltage, they have more turns on the secondary coil than the primary coil

Question 25

what does a step down transformer do

Answer 25

decrease the voltage, they have more turns on the primary coil than the secondary

Question 26

what are step up and down transforms used for

Answer 26

transmitting electricity across the country

Question 27

in power stations what are step up transformers used for

Answer 27

to boost the voltage before it is transmitted

Question 28

in power stations what are step down transformers used for

Answer 28

they are used at the end of the journey to reduce the voltage so its more useful and safer to use

Question 29

what is the ratio between the primary and secondary voltages the same as

Answer 29

the ratio between the number of turns on the primary and secondary coils

Question 30

in transformers how is an alternating voltage induced in the secondary coil

Answer 30

when the alternating voltage is applied across the primary coil, the magnetically soft core magnetises and demagnetises quickly