General

Question 1

How can insulators be charged by friction?

Answer 1

They are rubbed against each other, one becomes positive, the other negative

Question 2

How does charging by induction work?

Answer 2

An uncharged object placed near a charged object becomes charged as electrons are transferred.

Question 3

What is charging?

Answer 3

The gain or loss of electrons

Question 4

In which direction do magnetic field lines go?

Answer 4

From north to south to form closed loops

Question 5

What is the difference between hard and soft materials in terms of magnetism?

Answer 5

Soft materials gain and lose magnetisation very quickly

Question 6

What can cause a magnetic material to lose its magnetism?

Answer 6

Time
Hitting it
Heat

Question 7

What is the magnetic effect of a current?

Answer 7

Create magnetic fields in a surrounding space, so cause a compass to deflect from north. Degree of deflection depends on size of current. Reversing the current changes the deflection.

Question 8

Explain the right hand rule

Answer 8

A fist with the thumb point up
Thumb = direction current
Fingers = direction of field lines

Question 9

What is the magnetic field pattern of a coil and why?

Answer 9

Magnetic field created by each part of the coil combine to a create a strong field through the coil.

Question 10

Which end of a coil is clockwise or anticlockwise?

Answer 10

Clockwise = south pole
Anticlockwise = north pole

Question 11

Why is iron used as a core in magnets?

Answer 11

It is ferromagnetic
When an external magnetic field from a current-carrying wire or coil passes through a ferromagnetic material, the atomic magnets can line up with the external field to create a much stronger resultant field.

Question 12

How can you increase the magnetic strength of a solenoid?

Answer 12

Soft iron core
More turns per unit length
Increasing current

Question 13

What happens to a wire carrying a current in a magnetic field?

Answer 13

It experiences a force (motor effect)

Question 14

Explain the left hand rule

Answer 14

Forefinger = direction of magnetic field (N to S)
Middle finger = direction of current (+ to -)
Thumb = direction of motor effect force

Question 15

Unit for strength of magnetic field

Answer 15

Tesla

Question 16

What is F = BIL

Answer 16

F=BIL

F is the motor effect force in newtons (N).

B is the magnetic field strength in tesla (T).

I is the current in the wire in amps (A).

L is the length of wire at 90° to the magnetic field in metres (m).

The direction of the force is given by the left-hand rule.

Question 17

What is a split ring commutator?

Answer 17

Reverses the direction of current every half turn, allowing the motor coil to rotate continuously in one direction

Question 18

What happens when a wire cuts magnetic field lines?

Answer 18

A voltage is induced

Question 19

What does electromagnetic induction result in?

Answer 19

Always a voltage, a current if there is a closed circuit

Question 20

What factors affect the magnitude of an induced voltage?

Answer 20

The rate at which a wire cuts magnetic field lines

or

The rate at which the magnetic field through a conductor (eg a coil) changes

And the strength of the magnet

Question 21

In which direction is an induced voltage?

Answer 21

Against the direction of the change that caused it

Question 22

How can you increase the output of an AC generator?

Answer 22

Rotate coil more rapidly
Stronger magnetic field
Coil has greater area
More turns on coil

Question 23

What does a step up transformer do?

Answer 23

Increases the voltage

Question 24

A transformer has has more turns on the primary than secondary coil. What will the output voltage be?

Answer 24

Lower

Question 25

What is the equation for the coils and pds in a transformer?

Answer 25

Vp/Vs = np/ns

Question 26

What is the relationship between voltage and current in a transformer?

Answer 26

VpIp = VsIs

Question 27

Why are high voltages used in transmission lines?

Answer 27

Keeps current low, so reduced loss due to heating of the cables

Question 28

What is the equation for power wasted in a transmission line?

Answer 28

P=I^2 * R

Question 29

Do transformers work with AC or DC?

Answer 29

AC

Question 30

Why do we need to step down voltage?

Answer 30

Harder to insulate

Question 31

What is the equation for Hooke's law?

Answer 31

F=kx | Force applied = constant * change in length

Question 32

Equation for energy stored in a stretched spring?

Answer 32

E=1/2 k x^2

Question 33

What factors affect spring constant?

Answer 33

Greater cross sectional area = greater spring constant | Longer wire = smaller spring constant

Question 34

State newtons first law

Answer 34

A body will remain at rest or in a state of uniform motion in a straight line unless acted on by a resultant external force

Question 35

State newtons second law

Answer 35

force = mass × acceleration

Question 36

State newtons third law

Answer 36

If body A exerts a force on body B then body B exerts an equal and opposite force of the same type on body A

Question 37

What is the equation for momentum?

Answer 37

momentum = mass * velocity

Question 38

How does force relate to rate of change of momentum?

Answer 38

force = rate of change of momentum

Question 39

What is the equation for work done?

Answer 39

Work = force * distance moved

Question 40

What is the equation for GPE?

Answer 40

gpe = mgh

Question 41

What is the equation for kinetic energy?

Answer 41

1/2 m * v^2

Question 42

What is the equation for power?

Answer 42

energy transfer/time

Question 43

Why does temperature plateau?

Answer 43

For example at the melting point | All energy goes into breaking bonds

Question 44

In what three ways can heat be transferred?

Answer 44

Conduction Convection Radiation

Question 45

What is conduction?

Answer 45

particles pass on kinetic energy to their neighbours without actually moving

Question 46

What is convection?

Answer 46

This occurs when higher energy particles move to cooler regions, heating them up

Question 47

What is radiation?

Answer 47

heat transfer by the emission of infra-red electromagnetic waves

Question 48

How do you work out specific heat capacity?

Answer 48

shc = thermal energy / (mass * temperature change)

Question 49

What is the relationship between pressure volume and constant temperature?

Answer 49

PV = constant

Question 50

What is specific latent heat

Answer 50

specific latent heat of a substance is the amount of energy needed to change the state of 1 kg of the substance without changing its temperature

Question 51

What is specific heat capacity?

Answer 51

Specific heat capacity is defined as the amount of heat required to raise the temperature of 1 kilogram of a substance by 1

Question 52

What is the equation for specific latent heat?

Answer 52

E=mL | Energy transferred = mass * slh

Question 53

How do you work out hydrostatic pressure?

Answer 53

Hydrostatic pressure = hpg (height * density * gravity)

Question 54

What is a transverse wave?

Answer 54

the vibration direction is perpendicular to the wave direction

Question 55

What is a longitudinal wave?

Answer 55

the vibration direction is parallel to the wave direction

Question 56

How do you work out frequency?

Answer 56

1/period

Question 57

How do you work out wave speed?

Answer 57

distance/time | frequency * wavelength

Question 58

What happens when a light ray slows down?

Answer 58

Refracts towards the normal

Question 59

What happens when a light ray speeds up?

Answer 59

Refracts away from the normal

Question 60

What is the doppler effect?

Answer 60

When there is relative motion between a source of waves and an observer, the wavelength and frequency of the waves detected by the observer is different from the wavelength and frequency of the waves received when there is no relative motion

Question 61

Is the em spectrum longitudinal or transverse?

Answer 61

Transverse