Charlie’s Equations

Question 1

Work done, distance and force?

Answer 1

E = f d

Question 2

GPE

Answer 2

E(g) = g m h

Question 3

Power

Answer 3

E = P t

Question 4

Electrical Power (2 equations)

Answer 4

P = I V
P = I I R

Question 5

Specific Heat Capacity

Answer 5

E = m c (change in temp)

Question 6

Potential difference

Answer 6

Energy (J) transferred to each coulomb of charge.

Question 7

Ways to reduce energy dissipation?

Answer 7

Cavity wall insulation - insulation between walls.
Double glazing - vacuum inside window pane.

Question 8

Define ‘insulators’

Answer 8

Prevent unwanted thermal energy transfer.

Question 9

Define ‘thermal conductivity’

Answer 9

How effective something is at conducting heat.
Watts per meter Kelvin

K = P / (d k)

Question 10

Zero Error

Answer 10

A device doesn’t say 0 when it should.

Fixable

Question 11

Systematic error

Answer 11

Measuring equipment consistently produces a wrong value by the same amount of difference.

Fixable

Question 12

Random error

Answer 12

Unpredictable variation of data, naturally caused.

Non - fixable.

Calculate mean.

Question 13

Define a ‘solid’.

Answer 13

Regular arrangement.
Vibrates around fixed position.
Particles are close together.

Question 14

Define ‘liquid’

Answer 14

No regular arrangement.
Particles slide over each other.
Moderately close together.

Question 15

Define ‘gas’

Answer 15

No regular arrangement.
Particles move in a range of different velocities (random direction + speed).
Particles are spaced far apart.

Question 16

Efficiency Equation

Answer 16

Efficiency = (useful power output) / (total power input)

For AQA, answer must not be a percentage.

Question 17

Define ‘efficiency’

Answer 17

The proportion of energy that is transferred usefully. Not percentage for AQA.

Question 18

Number of electrons in a coulomb?

Answer 18

6.24 x 10^18

6,240,000,000,000,000,000

6.24 quintillion

Question 19

Curent, charge and time.

Answer 19

Q = I t

Question 20

Potential difference, energy transfer and charge.

Answer 20

E = V Q

Question 21

V, I and R

Answer 21

V = I R

Question 22

Define ‘resistance’.

Answer 22

How hard it is for current to flow.

The opposing force in result of electrical current.

Question 23

Define ‘Ohm’s Law’

Answer 23

Current is directly proportional to potential difference, if temperature remains constant.

Question 24

Resistors in series.

Answer 24

Sum of individual resistances.

Question 25

Resistors in parallel?

Answer 25

Total resistance is less than resistance of lowest resistors. When you add more resistors in parallel, total resistance decreases. 1/Rtotal = 1/ R1 + 1/R2 + 1/R3 … If values for all resistors are equal… Individual resistance / number of resistors = total resistance

Question 26

Transformer Equation

Answer 26

I(p) V(p) = I(s) V(s) P(p) = P(s) Coils on primary coil / coils on secondary coil = p.d.(p) / p.d.(s)

Question 27

Power loss equation?

Answer 27

P = I I R

Question 28

Direction of electric field of a positive charge?

Answer 28

Outwards. Force felt by a positive test charge.

Question 29

Effect on current when more components are added in parallel?

Answer 29

Current increases. P = I V

Question 30

Internal energy

Answer 30

Kinetic energy of particles. Potential energy between particles.

Question 31

Define ‘evaporation’

Answer 31

When a liquid becomes a gas. Can happen below boiling point: Faster-moving particles have enough energy to escape. Causes temperature to change, as mean energy of particles decrease.

Question 32

Specific latent heat equation?

Answer 32

E = m L

Question 33

Define ‘Pressure’

Answer 33

Force exerted per unit area.

Question 34

Pressure equation (force and area)?

Answer 34

F = P A

Question 35

Effect of heating on pressure?

Answer 35

Increased kinetic store of particles. They move faster. They collide with walls more frequently. Larger force per collision. Greater force per unit area. Greater pressure.

Question 36

Effect of decreasing volume on pressure?

Answer 36

Less distance particles need to travel. Collisions between particles and walls are more frequent. Greater force per unit area. Greater pressure.

Question 37

Effect of increasing number of particles on pressure?

Answer 37

More particles per unit area. Collisions between walls and particles more frequent. Greater force per unit area. Increases pressure.

Question 38

Boyle’s law equation?

Answer 38

P V = constant Only when temperature and number of particles remain constant.

Question 39

How to calculate uncertainty?

Answer 39

Find range. Divide by 2. Find mean. Uncertainty = mean +/- (range/2)

Question 40

Why does temperature increase when you decrease the volume of a gas quickly?

Answer 40

Force is applied on the gas, doing work on it. Work done is energy transferred. Energy is transferred to the internal store of particles, increasing kinetic energy of particles. Temperature increases.

Question 41

How penetrating is alpha radiation?

Answer 41

Can travel a few cm through the air. Blocked by a sheet of paper.

Question 42

Penetrating abilities of beta decay?

Answer 42

A few meters through air. Blocked by **5**mm aluminium.

Question 43

Penetrating abilities of gamma radiation.

Answer 43

Travels long distances. Stopped by a thick layer of concrete of lead.

Question 44

Describe the use of a cloud chamber to detect radioactivity.

Answer 44

Cloud chamber is full of supersaturated alcohol vapour. Ionising radiation leaves a trail of ionised molecules. Alcohol vapour condenses, showing the trail.

Question 45

How is a Geiger counter used to detect radiation?

Answer 45

Geiger muller tube is full of a low pressure gas. Atoms in the gas are ionised as radiation hits them, knocking electrons out of shells. The gas now conducts electricity. Current flows. Produces a clicking noise. Number of clicks = delays per second.

Question 46

How does photographic film detect radioactivity?

Answer 46

Bright spots appear where ionisation occurs.

Question 47

Most common isotope of hydrogen?

Answer 47

Protium. 99.98% common. Used in hydrogen fuel cells and plastic production.

Question 48

Deuterium uses?

Answer 48

Nuclear fusion. 0.02% common.

Question 49

Tritium uses?

Answer 49

Thermonuclear fusion weapons. Very rare.

Question 50

Factors that affect energy needed to heat a material?

Answer 50

Mass. Specific heat capacity. **Energy change**.

Question 51

What should you do when describing a graph?

Answer 51

Mention how the y-axis is affected by the x-axis.

Question 52

Alpha decay equation?

Answer 52

M 4 M-4 X ——-> He + Y P 2 P-2

Question 53

Beta decay equation?

Answer 53

M 0 M X ——-> E- + Y P -1 P+1

Question 54

Why do scientists repeat experiments?

Answer 54

To recognise and remove anomalies. To calculate a mean - reduces random error and increases accuracy.

Question 55

Define ‘activity’ in radioactive terms.

Answer 55

The number of radioactive decays that happen each second. Measured in Becquerels.

Question 56

Difference between count rate and activity?

Answer 56

Count rate is the number of decays counted from one area of a substance. They are directly proportional.

Question 57

What impact does a short half life have on irradiation of a substance?

Answer 57

Short half life. More unstable. Greater activity. More irradiation received when near.

Question 58

Why are some atoms radioactive?

Answer 58

The ratio of protons and neutrons are unequal, meaning it is unstable.

Question 59

Why are alpha particles used in smoke alarms?

Answer 59

**They are highly ionising, so ionises particles in the smoke alarm effectively**, allowing charge to be carried, completing the circuit, activating the alarm. **They are weakly penetrating, so irradiation cannot escape from casing and irradiate people.** **Has a long half-life, so maintains a constant count rate for a long time** and does not need to be replaced constantly.