RANDOM PPQ IGCSE PHYSICS PAPER2

Describe an experiment to investigate the shape of the magnetic field pattern of a bar magnet.

Any suitable method

Observe the needle -The line and the position of the needle of the compass is marked using a pencil and paper -Repeated for another line / in a different place OR o Place magnet under paper / plastic

Sprinkle iron filings over

Tap paper gently (to reveal pattern)

Describe a possible danger of fuelling an electrically-charged aircraft.

Fuel is flammable therefore electrical charge can ignite causing an explosion and fire.

Explain how an aircraft can become electrically charged while it is flying

Idea of electron transfer with Due to friction (Air resistance)

What electrical connection is made by the safety wire?

(Connect to) earth / earthing

Explain how connecting the safety wire reduces the possible dangers when fuelling an electrically-charged aircraft.

current flows in safety wire which discharges aircraft terefore aircraft becomes neutrol

Describe the difference between digital signals and analogue signals

Information is converted into BİNORY CODE (İMPORTANT) where it is converted into a series of electrical pulses that are sent down the telephone lines.

Information is converted into electical voltage or currents that varry conttinuously. These signals than are amplified.

(All signals become weak during transmission and need to be amplified)

Give one advantage of using digital signals.

may carry more information When a digital signals are amplified it creates a clean accurate copy of the original signal.

Use ideas about diffraction to explain why different frequencies require different sizes of loudspeaker.

Waves spread out (as they leave the speaker) (Different frequencies / notes have) different wavelengths Diffract most if speaker size matches wavelengthy

Independent variable = x Dependent Variable = y time is always = x Resistance= y

Suggest reasons why the student's conclusions might be incorrect.

There is a zero error

There could be reading error / parallax error The data on the tin may be wrong

The experiment was not repeated The weight of tins / bag was not taken into account

State ways in which the molecules in steam are different from the molecules in water.

More (kinetic) energy / more quickly / faster / further apart (in steam)/more freely

Explain how the molecules of steam exert a pressure on the inside of the kettle

IGNORE molecules hitting each other Moleucules are moving quickly and further apart collide with inside of kettle There is a force (on the inside)

pressure = force ÷ area

Units

1kHZ=1000 1A=1000mA 1kPa=1000Pa 1MW=1000000W 1kBq= 1000Bq 1MBq= 1000000Bq 1MJ=1000000J

The cylinder is turned off to stop more gas escaping. The temperature of the gas in the cylinder decreases. Explain what happens to the pressure of the gas in the cylinder.

Molecules move more slowly / have less kinetic energy Molecules hit sides less frequently and less force is produced per collusion Pressure is directly proportional to temperature. Pressure of the gas in the cylinder decreases

the kelvin temp is directly prop to the average kinetic energy of its molecules

You need to round it up or give the decimals.

State two factors that affect the stopping distance of a car driven on a road.

Road Weather-related e.g. wet / dry / rainy / icy

Surface-related e.g. gravel / mud / freshly Car Mechanical e.g. quality of tyres / brakes

Driver whether the driver is tired or influenced of alchol or drugs.

Use ideas about momentum to explain how the crumple zone of a car helps to reduce injuries during a crash.

-Car (and driver) take longer to slow down/time for crash increases -force is reduced since it is inversel prop with force when change in momentum is same which is same in this case. -Smaller force leads to less injuries.

Describe the process of controlled fission of U-235 in the nuclear reactor

Neutrons captured / absorbed by u-235

Causes break-up of nucleus Releasing energy Releasing neutrons Daughter nuclei These neutrons cause further fissions causing a chain reaction

Moderator to slow down neutrons since fissile material can only absorb slow moving neutron Control rod absorbs neutron to stop the chain reaction.

(Energy released) used to heat water to turn it to steam and with the steam turbine it is used as kinetic energy to convert to electrical energy with a generator.

Describe how Jenny's speed changed during the investigation.

slowed down/ Speed up

What feature of the graph shows this change?

(the line in the) graph becomes less steep

The droplets of paint are given the same charge as they leave the sprayer. Explain why this is an advantage.

(droplets) repel each other (droplets) spread out

The droplets of paint are positively charged. The object being painted is given a negative charge. Explain why this is an advantage.

(object) attracts droplets paint reaches obscured places/ tight corners less paint wasted/ not time consuming

Give one hazard caused by electrostatic charges and state how the risk from this hazard can be reduced.

risk of spark causing explosion

earth connection

Suggest why a runner might cool down too quickly if he does not wear a foil sheet.

evaporation as liquid = gas/vapour

higher (kinetic) energy/faster particles/molecules leave/ evaporate

reducing (average) energy of particles left /heat remaining

Reducing temperature

reducing temperature

Explain how the foil sheet reduces heat loss.

(shiny) reduces radiation /IR losses

Fisherman A and fisherman B feel different forces on their shoulders. Use ideas about moments to explain why fisherman A feels the larger force.

clockwise and anticlockwise moments equal

(and fish are) closer to A

so to get same moment for smaller distance (force must be larger)

Some power stations use uranium as a fuel. Describe the problems that arise from the disposal of waste from this type of power station

Radioactive / emits radiation

High activity

Long half live / need for long term storage

Danger / harm to people /environment

Expensive to contain / dispose of

Use ideas about particles to explain why the cooled balloon is smaller.

particles move at lower speed / lower kinetic energy

so hit sides less often / with less energy

reducing force / pressure

pulls balloon material into smaller size

I will change the temperature of the balloon by putting it into a freezer. To get a range of different temperatures I will put the balloon into the freezer for different times. I will measure the temperature of the balloon using a thermometer. To measure the size of the balloon I will take it out of the freezer and line it up next to a ruler. To make sure it is a fair test I will repeat the experiment three times. I will plot a graph of size against temperature.

There are several faults in the student's plan. Identify three of these faults and suggest an improvement to correct each one.

Fault #1 'different time in freezer' does not give range of temps / always cools to same temp

Improvement #1 Way to get range of temp

e.g use water bath(s)

use freezer(s) set to different temps Fault #2 Difficult /hard to 'measure temp of balloon with thermometer' OR this doesn't measure temp of gas inside

Improvement #2 Measure temperature of surroundings

e.g. inside of freezer

water bath or air Fault #4 'measure size next to ruler' is an inaccurate method / difficult to measure (with a ruler) IT IS 3D SHAPED Improvement #4 measure circumference using tape/string

State what is meant by the term magnetic field line

Line that shows direction of the magnetic field and space where magnetism can be detected around a magnet.

Describe the magnetic field.

Field is Uniform/or not Field direction is constont and field lines are parallel and are showing the same direction

If I measure all the coins at once and divide this value by the number of coins it will be more accurate. Do you agree with the student? Explain why

Good way of measuring small values Possible to make a maths erro Taking a larger measurement might reduce Not all coins are necessarily the same / idea of anomalous coin / bent / worn

The student wants to find the density of the coin. She uses her values for the diameter and thickness of the coin to calculate its volume. What else must she do to find the density of the coin?

Measure/find mass

Using a named instrument 'balance' A sensible experimental precaution: e.g. Repeat readings/ check balance zero

MP4 Formula to use (density = mass ÷ volume) MP5 A correct density unit mentioned (e.g. kg/m3)

How to obtain a more accurate value for the refractive index of glass?

-any mention of repetition / take an average of readings

-vary i to obtain more values -plot a graph of sin i against sin r -find gradient of graph

Why a fuse is important?

safety device / reduces danger In case of fault Prevents wires or appliance overheating

When the motor is working

the current in it is 1.74 A. Explain why it would not be sensible to replace the 13 A fuse with a 2 A fuse.

2A fuse would blow therefore would need to be replaced eachj time moter is turned on.

When a mopvement of an object stops or falls down

the ke is zero. However KE is at maximum just before it collides to earth where gravitational potential energy is fully converted to KE.

Why does falling over reduce the gravitational potential energy of the pbject?

Centre of gravity is lower

Explain why alpha particles and beta particles have different penetrating powers.

Alpha particles have less penetrating power /less range

Alphas have more charge

alphas cause more ionization alphas have more mass (kinetic) energy of alpha lost quickly since it collides with particles more frequently because of its mass and size and ionizing them.

The wet cloth sticks to tins 2 and 3 and they move away together.The student concludes: 'I threw the cloth the same way

so the velocity of tins 2 and 3 is the same as the velocity of tin 1.' Do you agree with this conclusion?Explain why.

Because variables are not controlled

e.g. mass of cloth different

mass of (other) tins different

Explain why beta particles are used

rather than alpha particles or gamma ray in a machine that measures the thickness of the allumibium foil.

Give one advantage of using wind turbines instead of a coal-fired power station to produce electricity.

No greenhouse gases Renewable (resource)

Coal-fired power stations are still in general use. Explain why wind turbines have not replaced them.

the wind does not always blow (at the right speed)

a large site is needed

a windy site is needed

one turbine produces less power than a power station

building a wind farm needs research and land therefore and takes time

Describe your line of best fit

Gradient / slope / correlation is positive or negative Line does / doesn't pass through origin (0

Does something increase as you increase sometihing

Suggest ways that the student could improve his measuring technique

take parallax into account parallel with scale closer to scale

Describe how the process of convection causes this air movement.

the air is warmed / heated (by the hot rocks)

air expands / molecules move apart

air becomes less dense hot air rises

(at height) air cools / contracts / becomes more dense

cooled air falls

From what point does this weight act?

Centre of gravity

Suggest two ways that this signal could be made to carry more information.

The idea of using increased bandwidth The idea of regeneration (AMPLİFYİNG) The idea of increased frequency ( Sends information faster) <

Explain what happens when a storm cloud discharges

there is a current Air conducts (Discharge) to earth

A student notices that the charger becomes warm when it is working. Suggest how this will affect the output of the transformer.

Energy lost Efficiency is not 100% It is because of resistance increasing which mean current passes harder tuning a lot of electrical energy to heat energy.

Describe how a teacher should measure the activity of a radioactive source using a Geiger-Muller detector

Before measuring the radioactive source put the radioactive source in a shield thick lead box using tongs and measure the background radiation. Since the GM detector is lined to ratemeter it will measure the background radiation. Since the GM detector is linked to ratemeter it will measure the number of ionising events happen per second and give a measure of the radioactivity in Bq (measure of how many disentegration happen per second). Than measure the radioactive source and substract the activity of background radiation from avtivity of radioactive source to find the activity of the radioactive source. Teacher should repeat the experiment to find the average and keept the distance between GM tube and radioactive source same and keep the time same as well.

Activity=Bq= Number of decays per second

What does 30 W tell you about the energy transfer in the soldering iron?

Power (rating) or watt(s)

2 Rate of energy transfer / joule per second / J/s

This soldering iron has an earth connection. Explain how an earth connection protects the user

When a fault occurs

fuse rating must be more than working current

EITHER Idea that 2.92 A is close to 3A

making 3A fuse a poor choice for soldering iron 'B'

OR Idea that 3A is much larger than 0.13 A

making 3A fuse a poor choice for soldering iron 'A'

Describe the structure of a step-down transformer. You may draw a labelled diagram to help your answer

In a step down transformer there is soft iron which links two coils. The number of coils in primary coil is bigger than the number of coils in secondary coil (input voltage/output voltage=number of turns in primary coil/number of turns in secondary coil)

Pin = Pout in 100% efficient transformers AC input voltage AC output voltage

Use ideas about particles to describe the changes that happen when a liquid boils to form a gas

Particles are moving much faster because they have more KE energy therefore they broke the forces of attraction between each particle which means there volume increase since they spread outand move more freely causing density to decrease.

) Explain how the vacuum reduces the thermal energy transferred to the liquid oxygen from the laboratory

(in a vacuum there are) no particles

so no conduction

so no convection (currents)

Suggest why a lid is not needed

gas is a poor conductor of ir/heat Idea that gas would build up pressure

Use ideas about momentum to explain why the load slides to the front when the lorry stops suddenly

(when the lorry stops) the load still has momentum