topic 11.2 supplying energy

Question 1

electromagnetic induction

Answer 1

The induction of potential difference in a wire which is experiencing a change in magnetic field.

Question 2

transformers change potential difference how

Answer 2

Use induction to change size of p.d. of an alternating current.
When alternating p.d. is supplied to the primary coil it produces alternating magnetic fields.
The Iron core gets magnetised due to the coil and the alternating magnetic field causes the magnetisation in core alternates.
The changing field induces a p.d. in the secondary coils.

Question 3

Vp = p.d. accross primary coil
Ip = current through primary coil
Vs = p.d. across secondary coil
Is = p.d. across secondary coil

Answer 3

Vp x Ip = Vs x Is

Question 4

Dynamos

Answer 4

generate Direct current
Generator apply force to rotate a coil in a magnetic field .
As coil spins current is induced.
current changes direction every half turn
Split ring commutator swap connection every half turn

Question 5

Alternators

Answer 5

Generate alternating current
work like dynamos.
has slip rings and brushes so the contacts don’t swap every half turn
Produces alternating p.d. and therefore alternating current

Question 6

microphones

Answer 6

uses electromagnetic induction to generate an electrical signal.
Sound waves hit diaphragm that is attached to coil of wire surrounding one pole of a permanent magnet and is surrounded by other pole.
As diaphragm moves a current is generated in coil.
Movement of coil depends on the properties of sound waves.
this is how microphone converts the pressure variables into variations in current

Question 7

Loudspeaker

Answer 7

Like microphones in reverse
Diaphragm replaced with paper cone.
Coil wrapped round pole of permanent magnet, so a.c. signal causes a force on the coil.
When current is reversed force acts in opposite direction.
Makes cone vibrate and make a pressure variation that causes sound waves.

Question 8

power equation

Answer 8

energy transferred / time taken

Question 9

electrical power equation

Answer 9

current x potential difference

Question 10

The power lost due to resistence heating

Answer 10

electrical power = (current x current) x resistence

Question 11

How powerstations produce energy

Answer 11

1)Uses a turbine to turn a huge alternator.
2)Burned fuels used to heat water and convert to steam that turn a turbine.
3)Turbine connected to powerful magnet in a generator- a huge cylinder wound with coils of copper wire.
4)as turbine spins magnet spins inducing a large p.d. and alternating current in coils.

Question 12

what is the Uk domestic supplyn

Answer 12

a.c at frequency of 50hz and a voltage of 230

Question 13

colours and names of wires in cables

Answer 13

live wire- brown
neutral wire - blue
earth wire - green and yellow

Question 14

potential difference between live and nuetral wire

Answer 14

equals supply p.d. ( 230 V for mains)