P4

Question 1

What are the two poles of a magnet?

Answer 1

North and South.

Question 2

What happens between like poles?

Answer 2

They repel.

Question 3

What happens between opposite poles?

Answer 3

They attract.

Question 4

What is a permanent magnet?

Answer 4

A magnet that is always magnetic and always has poles.

Question 5

What is an induced magnet?

Answer 5

A material that becomes magnetic when near or stroked by a permanent magnet. - temporary

Question 6

Which materials are commonly used as induced magnets?

Answer 6

Iron, Nickel, and Cobalt.

Question 7

What causes a material to become magnetised?

Answer 7

The alignment of domains within the material in the same direction.

Question 8

What do magnetic field lines show?

Answer 8

The direction and strength of a magnetic field — from north to south.

Question 9

What does a greater concentration of field lines indicate?

Answer 9

stronger magnetic field.

Question 10

What tool is used to map a magnetic field?

Answer 10

A plotting compass.

Question 11

What produces Earth’s magnetic field?

Answer 11

Currents in the Earth’s magnetic core.

Question 12

Why does a compass point North?

Answer 12

It aligns with Earth’s magnetic field lines.

Question 13

What is unusual about Earth’s magnetic poles?

Answer 13

The magnetic south pole is near the geographic North Pole (in Canada).

Question 14

What happens when current flows through a wire?

Answer 14

It produces a circular magnetic field around the wire.

Question 15

How is the direction of an electromagnetic field determined?

Answer 15

Using the right-hand grip rule.

Question 16

What increases the strength of this magnetic field?

Answer 16

Greater current and being closer to the wire.

Question 17

What is a solenoid?

Answer 17

A coil of wire with current flowing through it, producing a magnetic field like a bar magnet.

Question 18

What strengthens a solenoid’s magnetic field?

Answer 18

Inserting an iron core.

Question 19

What factors affect a solenoid’s magnetic field strength?

Answer 19

• Size of current

• Length of coil

• Cross-sectional area

• Number of turns

• Type of core

Question 20

What happens when two magnets interact?

Answer 20

They exert a magnetic force — attraction or repulsion.

Question 21

Why does a wire experience force near a magnet?

Answer 21

Because the magnetic field from the magnet and the field around the wire interact.

Question 22

What direction is the wire pushed?

Answer 22

At right angles to both the wire and the magnetic field.

Question 23

What does Fleming’s Left-Hand Rule show?

Answer 23

The directions of Force, Magnetic Field, and Current — all at 90° to each other.

Question 24

What does each finger represent for the Flemings left hand rule show?

Answer 24

Thumb - force direction
Pointer finger - field direction
Middle finger - current

Question 25

What type of current does the Fleming left hand rule use?

Answer 25

Conventional current — from positive to negative (opposite to electron flow).

Question 26

What is the formula for magnetic force?

Answer 26

F = B x I x L (Force = magnetic flux density × current × length)

Question 27

What is the unit of magnetic flux density?

Answer 27

Tesla (T) — number of flux lines per square metre.

Question 28

What do electric motors use?

Answer 28

A coil of wire between fixed permanent magnets.

Question 29

What happens to the coil in electric motors?

Answer 29

It rotates due to opposing magnetic forces on each side.

Question 30

Why does the coil rotate in an electric motor?

Answer 30

One side moves up, the other down due to induced magnetic forces.

Question 31

What causes a potential difference in a conductor?

Answer 31

A changing magnetic field causes electrons to move, building up charge.

Question 32

What happens if the conductor is part of a complete circuit?

Answer 32

A current flows.

Question 33

What direction is the induced magnetic field from the current?

Answer 33

In the opposite direction to the original field.

Question 34

What do electric generators use?

Answer 34

A rotating coil between two permanent magnets.

Question 35

What causes the coil to rotate in generators?

Answer 35

A turbine spinning the coil.

Question 36

What happens as the coil spins in a generator?

Answer 36

It cuts through the magnetic field, inducing a potential difference.

Question 37

What happens if the coil is in a complete circuit (generators)?

Answer 37

An alternating current (AC) flows.

Question 38

What is alternating current?

Answer 38

Current that constantly changes direction.

Question 39

What does changing direction of current also change?

Answer 39

The direction of the magnetic field produced.

Question 40

What type of current do transformers need?

Answer 40

Alternating current (AC).

Question 41

How does a transformer induce voltage?

Answer 41

The changing magnetic field from the primary coil cuts through the secondary coil.

Question 42

What happens in the secondary coil?

Answer 42

An alternating current is induced.

Question 43

What if the primary coil used direct current (DC)?

Answer 43

No voltage would be induced — no change in magnetic field.

Question 44

What happens in a step-up transformer?

Answer 44

The secondary coil has more turns, increasing the voltage.

Question 45

What happens in a step-down transformer?

Answer 45

The secondary coil has fewer turns, so voltage decreases.

Question 46

What is the transformer equation?

Answer 46

number of coils on primary/number of coils on secondary = p.d of primary/p.d of secondary

Question 47

When does the transformer equation apply to current?

Answer 47

Only if the transformer is 100% efficient.

Question 48

What do microphones produce?

Answer 48

A current proportional to the sound signal.

Question 49

What is inside a dynamic microphone?

Answer 49

A fixed magnet and a coil of wire that is free to move.

Question 50

How is current induced in a microphone?

Answer 50

Sound wave pressure variations move the coil, which cuts the magnetic field.

Question 51

What happens in a loudspeaker?

Answer 51

Current enters the coil → interacts with magnetic field → moves the coil and cone → produces sound waves.