P15 - Electromagnetism 2️⃣✅

Question 1

What is an alternator?

Answer 1

A generator that generates alternating current

Question 2

What is a dynamo?

Answer 2

A generator that generates direct current

Question 3

What is an electromagnet?

Answer 3

An insulated wire wrapped round an iron bar that becomes temporarily induced when there is a current in the wire

Question 4

What is electromagnetic induciton?

Answer 4

The process of inducing a potential difference in a wire by moving the wire so it cuts across/ through the magnetic flux/ field lines of a magnetic field

Question 5

What is flemings left hand rule used for, how does it work & what is each finger representative of?

Answer 5

A rule that shows the direction of a force on a current carrying wire in a magnetic field according to the directions of the current and the field and vice versa. Used for motors

Question 6

What is flemings right hand rule used for, how does it work & what is each finger representative of?

Answer 6

A rule that shows the direction of a force on a current carrying wire in a magnetic field according to the directions of the current and the field and vice versa. Used for generators

Question 7

What is the corkscrew rule used for, how does it work & what is each finger representative of?

Answer 7

(RIGHT HAND) Used to display directon of conventional current/ magnetic field. Used for magnetic fields

Question 8

What is the generator effect?

Answer 8

The production of potential difference using a rotating/moving magnet within a coil of wire/ magetic field

Question 9

What is induced magnetism?

Answer 9

Mangetism of an unmagentised material by placing it inside a magnetic field - can only attract not repel

Question 10

What is permanent magnetism?

Answer 10

Magetised materials that have a magnetic field and attract and repel materials

Question 11

What is magnetic flux density?

Answer 11

A measure of the strength of the magnetic field, the higher the magnetic flux density, the more powerfull the magnet

Question 12

What is the motor effect?

Answer 12

When a wire carrying a current creates a magnetic field which interacts with other magnetic fields causing a force

Question 13

What are the units of magnetic flux density?

Answer 13

T, Teslas

Question 14

What is a solenoid?

Answer 14

A long coil of wire that produces a magnetic field in and around the coil when there is a current in the coil

Question 15

What is conventional current?

Answer 15

When current travels from positive to negative, anticlockwise

Question 16

What does ANTS mean?

Answer 16

A lways
N orth
T o
S outh

Question 17

What is the shorthand notation for current flowing into a page?

Answer 17

Question 18

What is the shorthand notation for current flowing out of a page?

Answer 18

Question 19

Label this dynamo (d.c. generator)/ motor

Answer 19

Question 20

List 3 ways in which you could increase the induced voltage/ potential difference of a generator

Answer 20

1. Increase the current supplied/ bigger battery
2. Increase the number of loops in the coil
3. Increase the strength of the permanent magnet
4. Increase the speed of rotation of the coil

Question 21

Why is iron used for electromagnets not steel?

Answer 21

Because it’s magnetcially soft and can be magnetised quicker than steel. It would be a temporary magnet but steel would remain magnetised

Question 22

Label this Alternator (a.c. generator)

Answer 22

Question 23

A step up transformer ________ the voltage/p.d. and ________ the current

Answer 23

A step up transformer increases the voltage/p.d. and decreases the current

Question 24

A step down transformer ________ the voltage/p.d. and ________ the current

Answer 24

A step down transformer decreases the voltage/p.d. and increases the current

Question 25

What material is used for the core of a transformer and why?

Answer 25

Iron because its easily magnetised

Question 26

What is the purpose of the core of a transformer?

Answer 26

To transfer the alternating magnetic field from the primary to the secondary coil

Question 27

Why do transformers have to be alternating current (a.c.)?

Answer 27

Because the current needs to be capable of changing to allow for transformers to step up/ step down current

Question 28

How does a step up transformer work?

Answer 28

There are more coils on the secondary coil so the p.d. induced on the secondary is greater than primary, consequently stepping up the voltage /p.d. and decreasing the current (distributing small current reduces heat lost in cables making it more efficient)

Question 29

How does a step down transformer work?

Answer 29

There are less coils on the secondary coil so the p.d. induced on the secondary is less than primary, consequently stepping down the p.d. and increasing the current back to as it was. Voltage/p.d. stepped back down to 230 for national gird distribution

Question 30

How does a transformer work?

Answer 30

* Current supplied to transformer with the coil and iron core producing an alternating magnetic field * The magnetic flux/field is transferred through the iron core to the seconday coil * The coils on the secondary cut through the magnetic field in the iron core, consequently inducing a potential difference via electromagnetic induction

Question 31

What are loudspeakers?

Answer 31

Loudspeakers take electrical signals and use the motor effect to convert them into vibrations which then generate sound waves

Question 32

What are microphones?

Answer 32

Microphones detect vibrations caused by soundwaves and use the generator effect to convert them into electrical signals

Question 33

What type of current is used in microphones and loudspeakers?

Answer 33

Alternating current

Question 34

What is the function of a loudspeaker?

Answer 34

To convert electrical signals into sound waves

Question 35

What is the function of a microphone?

Answer 35

To convert sound waves into electrical signals

Question 36

Do loudspeakers rely on the motor effect or generator effect (electromagnetic induction)?

Answer 36

Motor effect

Question 37

Do microphones rely on the motor effect or generator effect (electromagnetic induction)?

Answer 37

Generator effect (electromagnetic induction)

Question 38

How do microphones work?

Answer 38

1. soundwaves hit the diaphragm 2. this causes the diaphragm and coil of wire to move 3. as the wire moves withthin the magnetic field of the permanent magenet it will generate a current via electromagnetic induction (generator effect)

Question 39

How do loudspeakers work?

Answer 39

1. An alternating current flows through the coil of wire and creates a magnetic field in the coil 2. the magnetic field in the coil interacts with the magnetic field of the permanent magnet 3. The interacting magnetic fields will exert a force on the coil (motor effect) causing it to move back and forth along the permanent magnet 4. This causes the cone to change shape 5. As the current is alternating (changing), the magnetic field and the force it experiences will also alternate; this means the coil of wire and cone rapidly move back and forth, oscillate, they vibrate 6. these vibrations form the cone are so fast that they create pressure variations in the air - which are the sound waves

Question 40

What 4 metals are magnetised?

Answer 40

* Iron * Steel * Nickel * Cobalt