ELECTROMAGNETISM & MAGNETISM

Question 1

magnet definiton

Answer 1

any material or object that produces a magnetic field

Question 2

where do field lines go from

Answer 2

north to south

Question 3

the closer together the field lines are …

Answer 3

the stronger the magnetic field is

Question 4

what is a permenant magnet

Answer 4

produces its own magnetic field

Question 5

examples of non contact forces to do w magnets

Answer 5

attraction & repulsion

Question 6

what is an induced magnet

Answer 6

a material that becomes a magnet when its placed in a magnetic field

Question 7

induced magnetism always causes …

Answer 7

a force of attraction

Question 8

magnetic field definiton

Answer 8

the region around a magnet where a force acts on another magnet or on a magnetic material

Question 9

strength of a magnetic field depends on…

Answer 9

the distance from the magnet

Question 10

how does a magnetic compass work

Answer 10

it contains a small bar magnet
the compass needle will point in the direction of the earths magnetic field

Question 11

How do you plot the magnetic field pattern of a magnet using a compass?

Answer 11

Place a bar magnet on paper.

Put a compass near one pole of the magnet.

Draw a dot at the tip of the compass needle (which shows the direction of the field).

Move the compass so the tail of the needle touches the dot.

Repeat steps 3–4 to trace the full field line.

Draw several field lines, starting from different points around the magnet to show the field pattern.

Question 12

magnetic elements

Answer 12

nickel
colbalt
iron
steel

Question 13

what is electromagnetism

Answer 13

where electric currents produce their own magnetic field when flowing through a conducting wire

Question 14

strength of electromagetic field depends on what

Answer 14

the current through the wire and the distance from the wire

Question 15

what is the right hand rule

Answer 15

curved fingers = show direction of the field lines / magnetic field
thumb = shows current

if current going upwards - thumbs up
if current going downwards - thumbs down

Question 16

electromagnetic field in a solenoid is

Answer 16

strong & uniform

Question 17

what is a solenoid

Answer 17

A solenoid is a coil of wire that produces a strong and uniform magnetic field when current flows through it

Question 18

adding an iron core to a solenoid does what

Answer 18

increases the strength of the magnetic field

Question 19

what is an electromagnet

Answer 19

a solenoid with an iron core

Question 20

true or false - the magnetic field around a solenoid and a bar magnet are similar

Answer 20

YES TRUE

Question 21

facts about solenoids

Answer 21

can reverse the magnetic field

Question 22

4 ways to increae the strength of a magnetic field

Answer 22

1. add iron core ( will become an induced magnet)
   2.incresse the current that flows through the solenoid
2. increase number of coils (keep length same)
   4.decrease the length (number of turns the same)

Question 23

motor effect definition

Answer 23

a current carrying wire in the presence of a magnetic field will experience a force

Question 24

motor effect more expained

Answer 24

when a conductor carrying a current is placed in a amgnetic field the magnet producing the field and the conductor exert a force on each other

Question 25

flemings left hand rule explained

Answer 25

thumb = force first finger = magnetic field second finger = current

Question 26

how to find strength of force

Answer 26

F = B * I * L

Question 27

the factors that affect the size of the force on the conductor

Answer 27

Magnetic field strength (stronger field = bigger force) Current in the wire (more current = bigger force) Length of wire in the magnetic field (longer wire = bigger force) Angle between wire and magnetic field - Force is maximum when at 90° / Zero when parallel to the field

Question 28

How does the force on a conductor in a magnetic field cause the coil in an electric motor to rotate?

Answer 28

A current flows through the coil in a magnetic field. The motor effect causes a force on each side of the coil (due to the interaction between the magnetic field and the current). The two forces act in opposite directions on each side of the coil (one up, one down). This creates a turning effect (moment), causing the coil to rotate. The split-ring commutator reverses the current every half turn, so the rotation continues in the same direction.

Question 29

What is an electric motor and how does it work?

Answer 29

An electric motor uses the motor effect to convert electrical energy into kinetic energy

Question 30

What causes the motor to spin?

Answer 30

A current-carrying coil in a magnetic field experiences a force on each side due to the motor effect. These forces act in opposite directions, creating a turning force (moment) that makes the coil spin.

Question 31

What does the split-ring commutator do?

Answer 31

It reverses the current every half turn, so the coil keeps spinning in the same direction.

Question 32

: How can you increase the speed or force of an electric motor?

Answer 32

Increase the current Use a stronger magnet Add more turns to the coil

Question 33

How do headphones use the motor effect to produce sound?

Answer 33

An alternating current (AC) from a device flows through a coil of wire inside the headphone. The coil sits in a permanent magnetic field. The motor effect causes the coil to move back and forth as the current changes direction. The coil is attached to a diaphragm (a small cone). As the coil moves, it makes the diaphragm vibrate. These vibrations create sound waves that travel to your ear.

Question 34

How does a loudspeaker work using the motor effect?

Answer 34

An alternating current (AC) flows through the coil. The direction of current constantly changes. The coil experiences a changing force, making it vibrate back and forth. The coil is attached to a cone (like paper or plastic), which also vibrates. These vibrations create pressure waves in the air, which we hear as sound

Question 35

how does the generator effect work

Answer 35

the process of generating electricity by moving a conductor (like a wire) through a magnetic field or by changing the magnetic field around a conductor. This induces a potential difference (voltage) and, if the conductor is part of a closed circuit, a current

Question 36

what does an induced current generate

Answer 36

a magnetic field around the conductor it flows through which opposes the change that caused the current to flow in the first place

Question 37

how to induce electromagnetic p.d

Answer 37

move an electrical conductor relative to a magnetic field or change the magnetic field around a conductor

Question 38

methods to change the size of the induced potential difference

Answer 38

1. stronger magnets = stronger magnetic field = larger p.d 2. move the wire/ magnets more quickly = magnetic field changes faster = bigger p.d 3. shape the wire into a coil = more turns = bigger p.d

Question 39

What affects the direction of an induced potential difference or current?

Answer 39

Direction of motion – Moving the conductor (e.g. wire or magnet) in the opposite direction reverses the current. Polarity of the magnetic field – Reversing the magnet’s poles (north ↔ south) also reverses the current.

Question 40

uses of generator effect

Answer 40

alternator - GENERATE AC dynamo - GENERATE DC

Question 41

how do alternators work

Answer 41

1. The coil of wire rotates relative to the magnets, this induces a magnetic field in the coil, which then induces a voltage and current in the coil. 2.The slip rings and brushes mean that the contacts don't swap every half turn (like they do in a motor or dynamo). 3.This means that they produce an alternating potential difference and an alternating current (a.c.). 4.As the coil rotates faster, the peaks of the oscillations get larger, and more frequent.

Question 42

how do dynamos work

Answer 42

1. As the coil of wire spins relative to the magnet, a magnetic field, and hence a voltage and current, is induced in the coil. 2.The split ring commutator means that the contacts swap every half turn. 3.This means that they produce a direct potential difference and hence a direct current (d.c.). 4.As the coil rotates faster, the peaks of the oscillations get larger and more frequent.

Question 43

how deos a microphone work

Answer 43

Sound waves (vibrations in the air) hit a diaphragm in the microphone. The diaphragm vibrates in response to the sound. This diaphragm is attached to a coil of wire, which is wrapped around a magnet. As the diaphragm vibrates, it makes the coil move in the magnetic field. This movement induces a voltage in the coil (via electromagnetic induction). The electrical signal created matches the pattern of the original sound wave. GENERATOR EFFECT

Question 44

function of a loudspeaker

Answer 44

It converts sound waves into electrical signals

Question 45

role of a transfromer

Answer 45

increase or decrerase the voltage of electricity

Question 46

what metal is used in transfromers

Answer 46

iron

Question 47

Vp/Vs =

Answer 47

Np/Ns

Question 48

how transformers work

Answer 48

1. alternating p.d is applied across the primary coil 2. causes a current to flow (also alternates) 3. generates a magnetic field around a coil (also alternates) 4. induces an alternating magnetic field in the iron core 5. induces a potential difference across the secondary coil 6. causes current to flow around secondary coil

Question 49

why is iron used in a transformer

Answer 49

its easily magnetised

Question 50

step up transformer

Answer 50

less turns on primary coil than secondary (twice as many(voltage=doubled))

Question 51

step down transformer

Answer 51

more turns on primary coil than secondary