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Question 1

How do dynamo generators work

Answer 1

Induce a current by spinning a coil of wire inside a magnetic field. As his happens pd is produced between the ends of the coil which causes current to flow

Spilt ring commutator that swaps be contact every half turn to keep current flowing as d.c

Question 2

How do ac generators work

Answer 2

One side of the coil moves up during one half turn and down on the other half turn. This means the coil is rotated in a magnetic field and alternating current is produced

Split rings and carbon brushes

Question 3

How do you strengthen a current

Answer 3

Rotate magnet faster
Add more coils
Add an iron core
Use a magnet with a strong magnetic field

Question 4

What do we use transformers for

Answer 4

Increase or decrease voltage of alternating currents

Question 5

How do transformers work

Answer 5

Voltage in one coil induces voltage in another

They use induction to change the size of pd of a.c current

Question 6

Transformer equation ?

Answer 6

Vp Np
— = —
Vs. Ns

Vp x np = vs x ns

Question 7

Define electromagnet

Answer 7

A coil of wire with a current flowing through it

Question 8

Define electromagnetic induction

Answer 8

The induction of pd and current if complete circuit in a wire which is experiencing a change in magnetic field

Question 9

Motor effect ?

Answer 9

When a current carrying conductor is placed in a magnetic field it will experience a force depending on the direction of the current a field

Flemings left hand rule

Question 10

What is Flemings left hand rule ?

Answer 10

Force = current x mganetic field x length

Thumb = force
First finger = magnetic field
Middle finger = current

Question 11

What are some uses of magnetic materials

Answer 11

Fridge doors- permanent magnetic keeps door closed
Cranes- induced electromagnets turn on and off to pick up stuff
MRI machine- magnetic field creates images
Doorbell- electromagnet turn on and off to attract and repel arm that hits a bell
Magnetic separators_ pick stuff up

Question 12

How does a step DOWN transformer work ?

Answer 12

Decrease voltage
Increase current
More turns in primary coil

Question 13

Describe how loudspeakers work ?

Answer 13

Coil wrapped round permanent magnet so the a.c signal causes force on coil and paper come moves. Current reversed = cone move backwards
Cone vibrates creating pressure creating a sound wave

Question 14

Define the national grid ?

Answer 14

A network of wires and transformers that connect UK power stations to its consumers

Question 15

Describe how microphones work ?

Answer 15

Sound waves hit flexible diaphragm attached to a coil of wire which surrounds a permanent magnet. The diaphragm and cp moves generating current from pressure

Question 16

Four magnetic materials

Answer 16

Iron
Nickel
Cobalt
Steel

Question 17

Give four ways you can induce the size of a current

Answer 17

Add more coils
Iron core
Increase field strength
Move magnet faster

Question 18

Define transformer

Answer 18

They step up and down a current but only work with a.c current

Voltage in one coil induces voltage in another

Question 19

What happens to some of the energy and why and how is it transported

Answer 19

High voltage low current it reduce be amount of heat loss and to maximise effeciency

Question 20

How does a step UP transformer work ?

Answer 20

Increase voltage
Decrease current
More turns on the secondary coil

Question 21

Define solenoid

Answer 21

a cylindrical coil of wire acting as a magnet when carrying electric current

Example of an electromagnet

Question 22

What three things does force depend upon ?

Answer 22

Field strength
Size of current
Length of conductor in the field

Question 23

How can current in a motor be reversed

Answer 23

Swap the poles

Swap polarity of the d.c supply