Past Paper corrections

Question 1

Give a reason for the difference in gravitational field strength on the moon and on the Earth ?

Answer 1

Earth has a larger mass than Earth

Question 2

Damages of infrared ?

Answer 2

Skin burns

Question 3

Explain why the ice cube will accelerate upwards when force (weight) is removed ?

Answer 3

1. Upwards force is greater than the weight of the cube
2. Resultant force is upwards

Question 4

Describe how the loudspeaker produces sound ?

Answer 4

1. Magnetic field around coil
   2.interaction between fields of magnet and coil
2. force on coil from magnet
3. Alt force on the cone
   5.Cone vibrates
4. Air to vibrate
5. Longitudinal wave

Question 5

Describe how total resistance changes when in series and in Parallel ?D4 - PPP

Answer 5

D4 - cell voltage is no longer shared means current through each loudspeaker is doubled so current from supply is 4 times higher
R = V/I

Question 6

Hazard of breathing sir contaminated with radon - 222

Answer 6

1. Irritation of internal organs
2. Highly ionising as it as alpha so can cause cancer /mutations

Question 7

As a container is cooled it collapses .Why

Answer 7

Fewer collisions per unit time gives lower force
Each collision is less hard
Lower force per unit area gives lower pressure
Pressure outside container is larger than pressure in the can
Pressure difference causes a force .

Question 8

Why does sign of the voltmeter change when the trolley moves ?

Answer 8

Direction changes so voltage depends on direction .End of motion ,voltage is 0

Question 9

Why does the magnitude of the induced voltage change ?

Answer 9

Speed may change
Magnetic field may not be uniform

Question 10

Explain the change in speed of parachute ?

Answer 10

Air resistance is larger than weight
F = MA
Acceleration is upwards
Air resistance decreases as parachutist slows down

Question 11

What is absolute magnitude ?

Answer 11

Measure of brightness of a star at a standard distance

Question 12

How to improve accuracy of an experiment ?

Answer 12

Graph and finding average

Question 13

Explain how a current is induced in the core of a transformer ?

Answer 13

1.Field lines cut by core
2.Induced voltage
3.Conductors have free electrons
4.Force on the electrons
5.Movement of electrons is current

Question 14

which type of radiation is emitted by radioactive nuclei with too many neutrons ?

Answer 14

Beta minus

Question 15

What is a longitudinal wave ?

Answer 15

A wave that travels parrellel to the direction the wave is moving in

Question 16

How is a nebulla formed ?

Answer 16

gas particles attract by gravitational force and temp increases and fusion reactions begin

Question 17

Describe the process of nucleur fussion in a star

Answer 17

Two small nuclei join together to form a large nucleus and relasess energy .

Question 18

What happens after main sequence ?MASS IS LARGER

Answer 18

red s=uoer gaint and ocntract rapidly becoming a supernova which emplodes and releases a neutron star pr black hole

Question 19

Why wires in toaster are connected in parrallel

Answer 19

Higher current or voltager

Question 20

KW to W

Answer 20

x1000

Question 21

How to measure volume with measuring cylinder

Answer 21

wait ffoir all the liquid to run down ,,place on horizontal surfaceread at eye level to avoid parralelex error

Question 22

Cat x - no fur and light skin
Cat Y - Thick fur and black
How do they transfer energy to their surrondings .

Answer 22

X loses more energy throuigh conduction and convention whereas Y loses through radiation .fur traps air ,poor conductor ,fur is a poor condutor ,trapped air reduces convection ,black surfaces emit radiation faster

Question 23

Explain where a lamp should be connected in this circuit so that the voltage across it increases as the light received by the component X decreases >

Answer 23

lamp should be connected in parallel with
component X / LDR;
resistance of LDR increases when it gets
dark;
voltage across LDR increases / becomes
greater than 10V when it gets dark

Question 24

Explain how dynamo causes the lioghts to turn on when bicycle is moving MAY2020

Answer 24

core gasins magnetic field ,CHANGING MAGNETIC FEILD ,feild lines are cut by wire ,voltage induces causing a current

Question 25

NOV 2020 - Why the egg moves down into the flask and then stops moving ?

Answer 25

air in flask cools; MP2. molecules in flask slow down/kinetic energy of molecules reduces; MP3. pressure inside flask decreases (as temperature decreases); MP4. pressure outside flask greater than inside/eq; MP5. resultant force (from air) pushes egg down the neck of the flask; allow ‘stretches egg’ MP6. volume of air in flask decreases as the egg moves down; MP7. (so) pressure inside flask increases (as volume decreases); MP8. (eventually) pressure inside and outside balance; MP9. (so) resultant force is now zero (so egg stops moving down);

Question 26

evolution of a star with a mass larger than the Sun

Answer 26

nebula/gas cloud; 5 MP2 protostar; MP3 main sequence (then red supergiant); MP4 supernova; MP5 neutron star/ black hole;

Question 27

when u drop a ball

Answer 27

MP1 ball has weight; REJECT ‘has gravity’ MP2 ball accelerates; MP3 drag increases (while accelerating); MP4 resultant force decreases; MP5 (so) acceleration decreases; MP6 drag = weight / resultant = 0 / forces balanced; MP7 terminal velocity/constant speed /acceleration=0;

Question 28

LDR resistence and lioght intensity is what grpah

Answer 28

non linear

Question 29

why does volatge decrease when resistnace decrese

Answer 29

larger current means larger voltage across fixed resistor; 2 total voltage remains constant;

Question 30

what is ionisation?

Answer 30

Removal of electrons from an atom

Question 31

what is used to make wire vibrate ?

Answer 31

AC

Question 32

Differnce between contamination and irradation - 2019

Answer 32

idea that contamination is when a non-radioactive object comes into contact with a radioactive material; 2 idea that irradiation is when radiation is present;

Question 33

Explain the conditions required for nuclear fusion.

Answer 33

MP1. high temperature required; MP2. to increase kinetic energy of nuclei; MP3. high pressure required; MP4. (because) nuclei need to be close enough to collide; MP5. (since) nuclei repel each other;

Question 34

Discuss how his measurements of voltage and current compare with the measurements when only one of these cylinders is used. DIFFERENCE OF PARALLEL AND SERIES

Answer 34

voltage stays the same; (because) each putty cylinder is connected in parallel (with the cells); total current doubles; (because) current in each putty cylinder stays the same (as before) and these currents add together; cuz there is two

Question 35

Why is a bar graphg used ?

Answer 35

Because the data is discountious

Question 36

The parachute jumper opens her parachute at point B. Her velocity decreases until she reaches terminal velocity again at point C. Explain this change in velocity.

Answer 36

air resistance increases (greatly) when parachute is opened; allow “upwards force” MP2. idea that air resistance is greater than the weight; allow upwards force is bigger than downwards force MP3. (therefore) deceleration / upwards acceleration; allow idea of upwards resultant force ignore “velocity decreases” MP4. idea that air resistance decreases with speed; MP5. resultant force (eventually) becomes zero; allow “forces are balanced again” allow air resistance = weight MP6. constant speed achieved

Question 37

Explain what happens to the wavelength of light when it passes from air into water. (2)

Answer 37

wavelength decreases; 2 (because) wave speed decreases and frequency remains constant;

Question 38

Differernce ebtrween the orbit of the comet and orbit of the earth

Answer 38

elliptical orbit and travels less distnace and the path is not fixed

Question 39

Describe an experiment to determine the refractive index of a glass block

Answer 39

measure angle of incidence / angle of refraction; MP5. repeat for different angle(s) of incidence; ignore unqualified ‘take repeats’ MP6. repeat for same angle of incidence; data analysis (2 marks max.) MP7. (use equation to) calculate n; no need to quote equation as it is requested in (c)(i) MP8. plot a graph of sin i against sin r; MP9. calculate n from gradient / calculate average value of n;

Question 40

longer distance mean resistance increases

Question 41

Explain why it is easier to cut vegetables with a sharp knife than with one that is not sharp.

Answer 41

pressure is force per unit area; sharp blade has smaller area; hence greater pressure (for the same force);

Question 42

how to improve accuracy of radiactive materials

Answer 42

remove background radiation

Question 43

2018 jan - why does the ice not melt

Answer 43

little conduction in liquids and gases hot water stays at the top because its less dense

Question 44

Explain why the balloons move towards each other when the student blows air between them. Refer to air speed and pressure in your answe

Answer 44

air (between the balloons) moves faster; 2 pressure (between the balloons) decreases/eq.

Question 45

The air in the tyre heats up when the car is driven. Explain how this affects the contact area between the tyre and the ground. [assume the volume of the air in the tyre remains constant]

Answer 45

particles move faster / have more KE;  particles hit (tyre) wall more frequently / with more force / harder;  pressure increases (and force of vehicle weight stays the same);

Question 46

Explain how this fission process can lead to a chain reaction

Answer 46

. more neutrons released (in fission); MP2. neutrons can be absorbed by other (uranium) nuclei; MP3. causing further fissions / splitting

Question 47

control rods

Answer 47

abopsrbs neutrons and vary the rate of reaction

Question 48

Suggest why there was an accident when the control rods were fully inserted into the reactor core.

Answer 48

graphite (ends) did not absorb neutrons; more (uranium nuclei underwent) fission; allow more ‘neutrons absorbed by (uranium) nuclei’ increased {rate of reaction / amount of energy produced / rate of fission};

Question 49

Cold water is pumped down into the hot, dry rock. Describe the energy transfers at each stage of electricity generation from this resource.

Answer 49

thermal energy is transferred from hot rock to cold water OR water heats up; MP2. water molecules gain KE (as they are heated); MP3. steam gains KE as it is heated by the rock; MP4. GPE of steam increases as it gains height; MP5. turbine gains KE from hot water/steam; MP6. generator (coils) transfer KE (from turbine) into electrical energy; MP7. electrical energy is transferred from pump into GPE/KE of water;

Question 50

Describe how the alternating current generates a sound wave.

Answer 50

alternating current changes direction (continuously); MP2. current in coil produces alternating magnetic field/eq; MP3. (producing) force on the coil/cone; MP4. reversing direction of current reverses direction of the force; MP5. hence coil/cone vibrates; MP6. cone vibrates air particles;

Question 51

Explain how the current produces movement of the coil.

Answer 51

MP1. Current in coil ; MP2. (Creates) magnetic field (around the wires of the coil); MP3. Interaction of (this) field with that of (permanent) magnets; MP4. There is a force on the wire(of coil); MP5. Reference to left hand rule; MP6. force up on one side and down on other side; MP7. Idea that commutator reverses current (every half turn)