Unit 12 & 13 - Magnetism And The Motor Effect/ Electromagnetic Induction

Question 1

What is a permanent magnet?

Answer 1

Something that is always magnetic

Question 2

What materials do magnets attract?

Answer 2

Magnetic materials

Question 3

Give 4 magnetic materials

Answer 3

Iron, steel, nickel and cobalt

Question 4

What is a magnetic field?

Answer 4

The space around a magnet where it affects other magnetic objects

Question 5

What are the full names for the ends of a magnet

Answer 5

North-seeking pole

South-seeking pole

Question 6

What is an induced magnet

Answer 6

When a magnetic material is in a magnetic field and becomes a magnet itself, it is no longer a magnet when it leaves the magnetic field

Question 7

Give 3 examples of how magnets are used

Answer 7

Electric motors, loudspeakers, knife holders

Question 8

What is used to find the shape of a magnetic field

Answer 8

Plotting compasses

Question 9

How do you use a plotting compass

Answer 9

Place near a magnet, mark the direction, use this point to line up next mark

Question 10

What type of magnetic field do 2 magnets form

Answer 10

A uniform magnetic field

Question 11

What is the earths magnetic field caused by

Answer 11

Electric currents in the molten outer core, nickel and iron

Question 12

What depends on the magnetic effect of electrical currents?

Answer 12

Electric motors

Question 13

What does the direction of the magnetic field depend on

Answer 13

Direction of current

Question 14

What rule is used for direction of magnetic field

Answer 14

Right thumb rule

Question 15

What does the strength of a magnetic field depend on

Answer 15

The size of the current

Question 16

What is a solenoid

Answer 16

When a wire is made into a coil

Question 17

What is the magnetic field shape of a solenoid

Answer 17

Uniform in the center and opposite directions outside

Question 18

What is an electromagnet?

Answer 18

A could of wire with a current flowing though it

Question 19

What cans strengthen the magnetic field of an electromagnet

Answer 19

Putting a piece of iron inside it

Question 20

What is the motor effect

Answer 20

When a force is produced as a result of a current carrying wire being between 2 magnets

Question 21

What happens in the motor effect

Answer 21

The current in the wire creates a magnetic field around the wire which interacts with the magnetic field between the magnets

Question 22

When is the force from the motor effect the strongest?

Answer 22

When the wire is at right angles to the magnetic field

Question 23

What rule shows the direction f the force from the motor effect

Answer 23

Fleming’s left hand rule

Question 24

What does each finger represent in the left hand rule

Answer 24

F - force
B - magnetic field
I - current

Question 25

What 3 factors does the size of the force from the motor effect depend on

Answer 25

Magnetic field strength Current size Length of the wire

Question 26

What is the strength of the magnetic field measured in?

Answer 26

Newton’s per amp metre (N/A m) | Tesla (T)

Question 27

What is the equation to calculate the force from the motor effect

Answer 27

F = B x I x L

Question 28

What is the role of a split ring commutator on an electric motor

Answer 28

To switch the direction of the current (each half is connected to an end of the coiled wire, as it turns, it constantly brushed past the + and - end of the circuit)

Question 29

How is a p.d induced on a wire

Answer 29

When a wire is moving into a magnetic field, however, if the wire stops moving (even in the magnetic field) there is no p.d

Question 30

What is caused as a result of a p.d being induced

Answer 30

A current

Question 31

Why are wires coiled in a magnetic field

Answer 31

So there is more current in the magnetic field so there is more current created

Question 32

What 3 factors affect the amount of p.d induced?

Answer 32

The number of coils, strength of the magnetic field, how fast the magnetic field changes of moved past the coil

Question 33

Besides a change in magnetic field, what can also induce a p.d

Answer 33

Is a wire is moved into a magnetic field

Question 34

How does reversing the direction of the movement of the magnetic field affect the direction of the p.d

Answer 34

It reverses the direction also

Question 35

What direction does a current flow

Answer 35

Out negative, in positive

Question 36

What direction does a magnetic field travel in

Answer 36

Out N in S

Question 37

What happens when a magnet is moving in and out of a coil of wire

Answer 37

A current is induced on the wire which creates it own magnetic field

Question 38

On a coil of wire that has a current induced, what makes one end of the wire N

Answer 38

If the N end of a magnet is moving into the coil

Question 39

What is the generator effect

Answer 39

When a conducting wire is moved into a magnetic field, a p.d is induced, if the wire is complete, a current is also created

Question 40

How does the generator effect produce an alternating current?

Answer 40

Since the edges of the coil are continuously switching direction, up the down, the direction of p.d is also switching. The p.d is 0 every time the coil is parallel to the magnetic field

Question 41

Why in an alternator are the ends of the wire connected to 2 different slip rings

Answer 41

To allow the current to pass out of the coil and change direction

Question 42

What are generators used in

Answer 42

Power stations

Question 43

What is a dynamo

Answer 43

A generator with a commutator

Question 44

How does a commutator work in a generator

Answer 44

The ends of the coil are connected to each half so when it spins, the direction of the current changes, causing it to always stay positive

Question 45

What do microphones do

Answer 45

They convert the pressure variations in sound waves into variations in current in electrical circuits

Question 46

How do microphones work

Answer 46

Sound waves cause variations in pressure, this makes a diaphragm vibrate, the diaphragm moves a coil of wire backwards and forwards which has a magnet inside it (a current is induced as a magnet moves in a wire)

Question 47

What is the national grid

Answer 47

A system of wires an cables that sends electricity to homes and schools from power stations

Question 48

Along the national grid, when is there the most energy wasted

Answer 48

Along the transmission lines

Question 49

What happens if the p.d is increased along the national grid

Answer 49

The current decreases

Question 50

Why are transformers used?

Answer 50

To change the p.d and current so less energy is wasted by heating

Question 51

What is a step-up transformer

Answer 51

A transformer that increases the voltage and decreases the current

Question 52

What is a transformer made of

Answer 52

2 coils of insulated wire wound into an iron core, no electrical connection between the coils

Question 53

What type of a current do transformers use

Answer 53

Alternating current

Question 54

How does a transformer work

Answer 54

Since there is a current supplied to the primary coil, a magnetic field is produced. The current alternates in direction so the magnetic field does also. The magnetic field is transmitted along the iron core and to the secondary coil. Since the mf is changing, a p.d is induced, causing a current to flow out the other end

Question 55

How does a step-up transformer work

Answer 55

There are more coils in the secondary coil than the first so when the p.d is induced, it is greater at the secondary coil, causing the current to decrease

Question 56

Why do transformers only work with ac

Answer 56

The current must change direction in order for a p.d to be induced

Question 57

What is the equation to work out the p.d in a transformer

Answer 57

PC p.d/ SC p.d = PC number of turns/ SC number of turns

Question 58

What is charge measured in

Answer 58

Coulombs

Question 59

What are the 3 equations for power

Answer 59

``` P = I x V P = E/ t P = I^2 x R ```