Magnetism

Question 1

Magnetism and magnetic materials

Answer 1

Magnets attract to objects containing iron, steel, nickel

Question 2

Magnetically hard

Answer 2

Hard to demagnetise, will retain magnetism once other magnet is removed
Steel

Question 3

Magnetically soft

Answer 3

Easy to magnetise and demagnetise but will lose magnetic ability when other magnet removed

Question 4

Magnetic fields

Answer 4

Symmetrical
Field lines close together at poles
No crossover
Hairy hamburger

Question 5

How to find magnetic field lines

Answer 5

Use plotting compass
Place compass on the end of one pole and put a dot where the tail of the needle is
Place compass tail on dot and put another dot on where the other side of the tail is
Repeat
Join lines together in a curve
N=>S

Question 6

Laws of magnetism

Answer 6

Similar poles repel
Opposite poles attract
Uniform magnetic field between poles

Question 7

How to make a magnet

Answer 7

Atom, tiny magnet called dipole
Many dipoles, domain
If unaligned, domains cancel out
If domains line up, magnetic

Question 8

Electromagnetism

Answer 8

Magnetic field will be established around current carrying wire
Circular magnetic field

Question 9

Right hand grip rule

Answer 9

Thumb, current
Fingers, field direction
Dart needle, towards
Tail away

Question 10

Magnetic field around a solenoid

Answer 10

Solenoid has north and South Pole

Like a bar magnet

Question 11

Solenoid can be strengthened by

Answer 11

More coils
Iron core
More current

Question 12

Uses of electromagnetism

Answer 12

Relays, small voltage used to switch a larger cola tape appliance on
Circuit breakers, circuit broken if excess current flows caused by malfunction
Electric bell
Loudspeaker, uses AC and permanent magnet to cause movement

Question 13

The motor effects

Answer 13

When 2 field lines cross, wire experiences a force when in a magnetic field
FLHR
Force on charged particle when it moves in a magnetic field as long as the motion is not parallel to the field

Question 14

FLHR

Answer 14

Thumb, motion
First finger, field
Second finger, current

Question 15

How to change the direction of induced force

Answer 15

Flip the battery

Flip the magnet

Question 16

How to increase the force induced

Answer 16

Add more current
Increase magnetic field strength
Increase no of wires

Question 17

Generators

Answer 17

Convert mechanical energy into elec energy

Question 18

DC motor

Answer 18

Converts electrical energy and magnetism into movement
N=>S
Coil rotates, cuts through field lines
Induces current in coil
1 terminal, always +
1 terminal, always -
Direction of current does not change
Split rings rotate with coil

Question 19

Increase motor strength

Answer 19

More coils on rotating part
Increase current flow
Increase magnetic strength
Increase area of coil

Question 20

Electromagnetic induction

Answer 20

Is a wire is moved through a magnetic field, a current is produced
Induction also occurs if a magnet is moved in a coil of wire or if a coil of wire rotates in a magnetic field
KE=>electrical
Faster movement, higher pd generated

Question 21

FRHR

Answer 21

Thumb, motion
First finger, magnetic field
Second finger, current

Question 22

How would movement of magnet affect galvanometer

Answer 22

More KE=>more elec energy, galvanometer will show more current
Change direction, change direction of current
More coils, more induction of current
Stronger magnet, greater induced current
No movement, no change on galvanometer

Question 23

AC generator

Answer 23

Magnetic field from N=>S
Cutting through magnetic field lines as coil rotates which induces a current in coil
FRHR shows that current is in diagram
One slip ring, +
Other slip ring,-
Half a cycle later, coil in field has rotated 180, reverses current in circuit

Question 24

How to increase voltage in generators

Answer 24

Spin it faster
Stronger magnet
Larger number of coils
Larger area of coils

Question 25

Transformers

Answer 25

Transforms AC voltage to a different value Step up and step down AC produced a continually changing magnetic field within the iron core, Magnetic field indices a voltage in the secondary coil which induces a current

Question 26

Energy waste from transformers

Answer 26

Heat wasted, current flows through Magnetic field in core produces eddy currents, cause heating Iron core, laminated to reduce eddy currents Magnetic field may leak out of core if there is a gap between the p and s

Question 27

What happens when transformation happens

Answer 27

Voltage stepped up, after it has left the power station, vvvvv low current Voltage stepped down as sub stations, current increases

Question 28

The National Grid

Answer 28

Boiler, turbine, generator, transformer Low current, less power loss through heating P=I^2R