|State the purpose of the fuse fitted in the plug of an appliance.
|stops too large a current
OR prevents wiring overheating
OR protect wiring (from damage)
|Explain in terms of electron flow what is meant by alternating current.
|direction of electron (flow)
(continually) changing back and forth/to and fro
|What happens to the power when the when R added in parallel?
|(power dissipated is) greater/increased/higher (combined/parallel/total) resistance less voltage across motor is greater/increased OR current (in motor) is greater/increased
|Using the kinetic model, explain what happens to the pressure of the air inside the pump as its volume decreases.
|(individual) particles collide with container/walls more frequently (than before) (overall) force (on walls) is greater pressure increases
|Suggest how the accuracy of the frequency determined by the student could be improved.
|measure the time for more waves to pass
OR count the number of waves in a longer period of time
OR repeat (the measurement) and average
|State what is meant by an activity of 80 kBq.
|80 000 (nuclei) decay(s) per unit time
|Explain how a single reaction can lead to the continuous generation of energy.
|neutrons can go on to cause further (fission) reactions/split more (uranium) nuclei causing a chain reaction/this process repeats
|Use of NUCLEAR RADIATION
|any suitable use (eg treating cancer/tracers/ sterilisation/smoke detectors/ measuring thickness of paper)
|Describe how the upward force exerted by the weightlifter on the barbell compares to the weight of the barbell.
|(The forces are) equal (in size) and opposite (in direction).
|State a suitable detector of visible light
|State the speed of the radio waves.
|3.00 ´ 10 8 ms -1
|State what is meant by the term gamma rays.
|High frequency (or short wavelength) electromagnetic radiation
|The radioactive source must be stored in a lead-lined container.
Explain why a lead-lined container should be used.
|Lead can absorb (some of) the gamma rays
|State the annual effective dose limit for the radiation worker.
|Explain why the phone receives a signal at X but not at Y.
|The waves from the transmitter will diffract over the hill to reach X but will not diffract enough to reach Y
|Using the kinetic model, explain the increase in the pressure of the gas in the syringe as its volume decreases.
|As volume decreases, the particles of gas will strike the piston of the syringe more often Since P= F/A , this results in an increased pressure
|Explain how the graph confirms that Xis directly proportional to Y.
|The line of best fit is a straight line
which passes through the origin
|Explain how this [ LDR Mosfet ] circuit works
|Light level increases, LDR resistance decreases
LDR resistance decreases, voltage across R increases
Voltage across R increases, MOSFET switches the motor on
|State how the frequency of microwave radiation compares to the frequency of infrared radiation.
|(Microwave radiation has a) smaller (frequency than infra-red radiation)
|State whether the orbital period of the ISS in its highest orbit will be less than, the same as, or greater than the orbital period calculated in part (d) (i).
|(Orbital period will be) greater
|Explain, in terms of forces, how the parachutes reduce the speed of
|Upward force is increased (by parachutes) producing an unbalanced force upwards
|Explain why these Modules burn up on re-entry into the atmosphere.
|Force of friction is created on the surface of the modules causes heat to be produced
|Explain why in hilly regions you can receive radio but not TV signals
|Radio waves are longer in wavelentgh than TV waves and longer waves diffract more than waves with a shorter wavelength
|State the speed of microwave signals in air
|3 x 10⁸ m/s or 300,000,000m/s
|What is meant by the term geostationary
|Orbits at 36000km above the equator OR same period as earth
|State a reason for a commercial motor using field coils instead of permenant magnets
|Motor has a smaller mass OR field can be controlled OR can be used in AC/DC OR can be switched off
|State a reason for a commercial motor using a multi section commuter instead of a single commuter
|Motor is more powerful OR turns more smoothly
|A student has an eye defect. An object close to the students eye appears focoused but a distant object appears blurred. What name is given to this eye defect?
|Myopia or short sight
|State what is meant by thr term ionisation
|When an atom gains negative charge OR when an atom loses negative charge. OR when an atoms gains electrons OR when at atom loses electrons
|State the unit of equivalent dose
|sieverts/Sv OR mSv
|Suggest a suitable output that will illuminate the warning display (on a car)
|Explain in terms of forces, why seatbelts are used in cars
|The driver will continue to travel at a constant speed until the seatbelt applies an unbalanced force to stop the driver
|The temperature outside the car is measured with an electronic thermometer and displayed on a screen. What input device could be used in the electronic thermometer?_x000D_
|State what is meant by gravitational field strength
|Weight per unit mass
|Which radiation in the EM spectrum has the shortest wavelength
|State one detector of radio waves
|Thermograms OR electronic thermometer
|Describe how signals are transmitted along optical fibres.
|(Light travels through the glassfibre.) Rays of light are(totally internally) reflected
(inside the fibre) OR: “TIR”
|State one advantage of using optical fibres rather than copper wires for transmitting signals.
|Carry more information OR
better signal quality
|Explain why the mains switch must be connected to the live cable from the mains supply.
|To switch off all circuits OR To isolate the consumer unit fuses and domestic circuits from the mains supply
|State another difference between the ring circuit and the lighting_x000D_
|The lighting circuit uses thinner
|State one advantage of using a ring circuit as a preferred method of wiring in parallel.
|Two routes for current to flow/less
(half) current in each branch
Easier to add more sockets
Less voltage drop
DO NOT accept:
Safer (unless qualified by “less current”)
Any comparison with series circuit
Less current per ring
All sockets get 230 V
|State one advantage of using a circuit breaker instead of a fuse.
|Reusable/faster response time/
Easier to tell if on or off
‘Trips’ at a smaller overload
Fuse needs to be replaced
Switches off “immediately”
DO NOT accept:
|State one further safety precaution that should be taken by the teacher when handling the radioactive sources.
|Use forceps/don’t point at eyes/
wear gloves etc
|Describe one medical use of radiation where the radiation is used to destroy cells.
|Instrument sterilisation/treatment of_x000D_
|Explain how this circuit operates to activate the motor in the dryer when the light level falls below a certain value.
|R of LDR increases (½) V across LDR increases_x000D_
(above 0·7V) (½)_x000D_
Transistor switches ON (½)_x000D_
Relay coil is energised_x000D_
(which closes the relay switch_x000D_
and activates the motor) (½)
|Name a suitable output device that could be used in the alarm box to produce an audio output.
|When one of the inputs_x000D_
(to gate X) is logic 0/OFF/_x000D_
The output (from gate X) is_x000D_
|Explain, in terms of Newton’s Third Law, how the rocket engines propel the rocket upwards.
|Engine/exhaust gases pushed down_x000D_
(A on B); gases push rocket up_x000D_
(B on A)_x000D_
|Explain why larger aircraft require a longer runway to land safely.
|Aircraft has increased mass 1_x000D_
so has reduced deceleration 1_x000D_
Aircraft has increased kinetic energy 1_x000D_
w E = Fd (so if F is constant d is greater) 1
|Explain why these Modules burn up on re-entry into the atmosphere.
|Force of friction is created on the_x000D_
surface of the modules 1_x000D_
causes heat to be produced 1
|Explain, in terms of forces, how the parachutes reduce the speed of the Module.
|Upward force is increased (by_x000D_
producing an unbalanced force_x000D_
|Explain, in terms of its horizontal velocity and weight, how the ISS remains in orbit around the Earth.
|The horizontal velocity of the ISS is_x000D_
large enough to ensure that it does_x000D_
not get closer to the Earth’s_x000D_
surface (or equivalent statement) 1_x000D_
The weight of the ISS is large_x000D_
enough to ensure that it does not_x000D_
move further away from the Earth’s_x000D_
surface (or equivalent statement) 1
|State how the frequency of microwave radiation compares to the frequency_x000D_
of infrared radiation.
|(Microwave radiation has a) smaller_x000D_
(frequency than infra-red radiation)
|The MOSFET switches on when the voltage across variable resistor R reaches 2·4 V. Explain how this circuit works to close the blind.
|Light level increases, LDR_x000D_
resistance decreases 1_x000D_
LDR resistance decreases, voltage_x000D_
across R increases 1_x000D_
Voltage across R increases,_x000D_
MOSFET switches the motor on 1
|Explain why the actual time taken to make the ice will be longer than the time calculated in part (c) (i).
|Heat will be taken in from the_x000D_
so the system will have additional_x000D_
heat to remove 1
|Using the kinetic model, explain the increase in the pressure of the gas in the syringe as its volume decreases.
|As volume decreases, the particles_x000D_
of gas will strike the piston of the_x000D_
syringe more often 1_x000D_
Since P= F/A , this results in an_x000D_
increased pressure 1
|When carrying out the experiment, the student clamped the syringe rather than holding it in their hand._x000D_
Explain why this is better experimental practice.
|Using a clamp will prevent heat_x000D_
from the student’s hand increasing_x000D_
the temperature of the gas in the_x000D_
If the temperature of the gas in the_x000D_
syringe is not constant, the_x000D_
experiment would not be valid 1
|A second student suggests that replacing the short tubing between the syringe and the pressure sensor with one of longer length would improve the experiment._x000D_
Explain why this student’s suggestion is incorrect.
|The suggestion is incorrect because_x000D_
the volume of air in the tubing is_x000D_
not being read from the scale on_x000D_
the syringe 1_x000D_
A longer length of tubing would_x000D_
increase the (systematic)_x000D_
uncertainty in the experiment 1
|The climber also carries a mobile phone. The climber notices that the phone receives a signal at X but not at Y._x000D_
Explain why the phone receives a signal at X but not at Y.
|The waves from the transmitter will_x000D_
diffract over the hill to reach X 1_x000D_
but will not diffract enough to_x000D_
reach Y 1
|Explain why this method (half-life) could not be used to estimate the age of a tree that died 100 years ago.
|The activity (of a sample from the tree)_x000D_
would not have reduced significantly/_x000D_
measurably in 100 years
|(As orbit is circular) direction changes / or unbalanced force exists so velocity changes .
|Although the satellite travelled at a constant speed in a circular orbit, it accelerated continuously. Explain this statement._x000D_
|Car continues at a constant speed during this time. AB represents driver’s reaction time OR the forces are balanced (orequivalent).
|Describe and explain the motion of the car between A and B.
|Less than. Some heat is lost to surroundings.
|Is the actual temperature change of the ball greater than, the same as or less than the value calculated in part (a)(ii)? You must explain your answer.
|Answer= 3.42 This is greater than the 3W or labelled power rating (so it overheats).
|During this experiment, the resistor becomes very hot and gives off smoke. Explain why this happens
|No. In parallel the voltage is still the same/6V across each resistor so its power is the same
|The student states that two of these resistors would not have overheated if they were connected together in parallel with the battery._x000D_
Is the student correct? explain your answer_x000D_
|As the temperature increases the resistance of thermistor RT decreases. What happens to the voltage across RT as the temperature increases?
|The temperature of RT now decreases.
Will the lamp stay on or go off?
You must explain your answer.
Temperature decreases, resistance increases, voltage drop increases to be >2.4V. Circuit switches on.
|A student standing beside the apparatus observes the beeps and flashes happening at exactly the same time. Another student 88 m away does not observe them happening at the same time.
|The speed of sound is less than the speed of light.
|Optical fibres are used to carry internet data using infra-red radiation. Is the wavelength of infra-red radiation greater than, the same as, or less than the wavelength of visible light?
|The diagram shows the path of the infra-red ray as it passes through a section of the fibre, name the effect shown.
|Total Internal Reflection
|More amplitude recieved at the microphone
|Explain why using the curved reflector makes the sound detected by the_x000D_
|The spy needs spectacles to see distant objects clearly._x000D_
What is the name given to this eye defect?
|What type of lens is needed to correct this defect (short sightedness?
|weapons, rocks, atmosphere
|State two factors which can affect the background radiation level.
|A type of electromagnetic radiation / wave/ ray.
|The source emits gamma rays. State what is meant by a gamma ray.
|The moderator slows neutrons.
|In a nuclear reactor, state the purpose of:_x000D_
|The containment vessel prevents/reduces release of_x000D_
radiations OR radioactive gases OR radioactive substances etc.
|the containment vessel.
|Fission or Chain reaction.
|What type of nuclear reaction takes place in a nuclear power station’ s reactor?
|The accepted value for the density of air at this temperature is 1·29 kg m–3. Explain why the technician’s answer is different from the accepted value.
|Not all the air will be evacuated from jar OR It is impossible to get a perfect vacuum OR Some air has leaked back in
|Use the kinetic model to explain this change in pressure after removing air with the syringe.
|Particles collide with walls of jar. Number of collisions on walls of jar is less frequent. Average force (on walls) decreases. Pressure on walls of jar decreases
|Explain why the reading on the voltmeter has decreased
|(Total) resistance decreases (circuit) current increases, lost volts increases
|Explain what is meant by a capacitance of 200 µF.
|200 µC of charge increases voltage across plates by 1 volt OR 200 µC per volt OR One volt across the plates of the capacitor causes 200 µC of charge to be stored
| The distance between the two foils is now increased and the experiment repeated. Explain why this gives a more accurate result for the acceleration due to gravity.
|Percentage fractional uncertainty in measuring distance will be smaller OR percentage fractional fractional uncertainty in measuring time will be smaller
|Explain why the output voltage Vo does not increase above 13 V.
|output cannot be greater than approx 85% of the supply voltage OR saturation of the amplifier has been reached
| Explain why the kinetic energy of the electrons is zero below the frequency f₀
|Photons with frequency below f₀ “because f₀ is threshold do not have enough energy to release electrons OR Photons with frequency below f₀ have energy smaller than work function
|gamma radiation can penetrate the body OR as beta radiation cannot penetrate the body
|Explain why Iodine-123 should be used as a tracer to diagnose problems in the thyroid gland.
| (As temp increases,) input voltage to transistor increases (½) (above 0·7V) switching transistor on (½) Current in the (relay) coil (producing magnetic field). (½) (Relay) switch closes / activates, (½) (completing the bell circuit/ operating the bell).
|Explain how the circuit operates to sound the bell when the temperature of the thermocouple reaches a certain value.
|Energy is lost as sound OR heat (within the transformer coils/core.)
|State one reason why transformers are not 100% efficient.
|It moves with constant speed in the horizontal direction (1) while accelerating due to the force of gravity in the vertical direction (1)
|The ISS orbits at a height of approximately 360 km above the Earth. Explain why the ISS stays in orbit around the Earth.
|direction of electron (flow) (continually) changing back and forth/to and fro
|The blender is connected to an alternating current (a.c.) supply. Explain in terms of electron flow what is meant by alternating current.
|(power dissipated is) greater/increased/higher (1) (combined/parallel/total) resistance less (1) voltage across motor is greater/increased OR current (in motor) is greater/increased (1)
|State the effect that closing switch S2 has on the power dissipated in the motor. Justify your answer.
|(individual) particles collide with container/walls more frequently (than before) (1) (overall) force (on walls) is greater (1) pressure increases (1)
|Using the kinetic model, explain what happens to the pressure of the air inside the pump as its volume decreases.
| The rocket engine in a spacecraft burns fuel producing exhaust gases. Identify the Newton pair of forces
|The spacecraft (or equivalent) pushes the exhaust gases (backward). The gases push the spacecraft (or equivalent ) ( forward.)
|State the energy transformation in the filament lamp.
|Electrical ---> light + heat
|Filament lamps and LEDs are examples of output devices. Name one other output device.
|Any suitable – heater, motor, (loud)speaker, relay, etc.
|Explain in terms of electron flow what is meant by alternating current (a.c.).
|The flow of electrons constantly changes direction
|Explain why the guitar string induces an a.c. voltage.
|The string changes direction (in the magnetic field.)
|Name the effect used to transmit light through a glass optical fibre.
|Total internal reflection
|The worker wears a badge containing photographic film. Explain how this can indicate if the worker has been exposed to radiation.
|Photographic film will) fog / darken (when exposed to radiation).
|X-rays can cause ionisation. Explain what is meant by ionisation.
|When an atom gains / loses (orbiting) electrons.
|Use the kinetic model to explain what happens to the pressure of the gas as its temperature decreases.
| as temperature decreases the particles slow down/lose Ek . strike the sides of the container less often. each collision less forceful/hard. pressure decreases. Reference must be clearly about the force of the individual particle collisions eg “the particles move more slowly and so strike the walls less often, meaning the force is less and so the pressure is less”
| Using the terms electrons, holes and photons, explain how light is produced at the p-n junction of the LED.
|(When the LED is forward biased) holes and electrons (re)combine (at the junction ) (of the LED) and photons (of light) are produced/emitted.
|Explain why a spectrum is produced in the glass prism.
|Different frequencies / colours are refracted through different angles OR different frequencies / colours have different refractive indices
|State what is meant by the resultant of a number of forces.
|A single force which will have the same effect as all the other forces
|The parascender releases the rope and initially rises higher. Explain, in terms of the forces acting, why the parascender rises.
|The vertical component of the force exerted by the parasail is greater than the weight of the parascender.
| Explain what happens to the density of the trapped air when its temperature is increased.
|remains the same neither the mass nor the volume have changed
|Capacitors have an insulator between their plates. Explain why there is a current in the circuit during the charging process.
|Electrons flow in all the wires because they are repelled from negative terminal of power supply to bottom/one plate of the capacitor and they are attracted off the top/other plate towards positive terminal of power supply
|At the end of the run, the engine is switched off and parachutes attached to the car slow it down. Explain how the parachutes slow down the car.
|Parachute creates friction (which acts in opposite direction to motion)
|Explain the difference between conductors and insulators.
|Conductors allow charges to move and insulators do not
|Explain what a.c. and d.c. mean in terms of current.
|a.c. − Current changes direction continuously (1) d.c. − Current is in one direction
|Is the wavelength of the ultrasound in the tissue longer, shorter or the same as it is in air? Explain your answer.
|Longer (1) frequency same but velocity greater
|Which radioactive source should be used? You must explain your answer
| Source X: (1) beta is required (owing to the range/some of it would be absorbed by the paper) (½) with a long half-life
|Explain the function of the moderator
|In practice the acceleration is not constant. Give a reason for this.
|Other forces will act on the plane, mass decrease
| State the speed of ultrasonic waves in air
|What happens to the lost kinetic energy?
|Turns into heat energy
|State what is meant by the term voltage.
|(The voltage of a supply is a measure of) the energy given to the charges in a circuit.
|State how this affects the speed of the motor compared to Circuit 1. Explain your answer
|The motor speed will reduce. The (combined) resistance (of the circuit) is now higher/current is lower. Voltage across motor is less Motor has less power
| What is the purpose of component X in the circuit?
|To act as a switch
|What is the purpose of the variable resistor R in this circuit?
|The variable resistor is to set the light level at which the transistor will switch on or to set the level at which the buzzer will sound
|Light waves are transverse waves. Sound waves are longitudinal waves. Describe each type of wave in terms of vibrations.
|With transverse waves the vibrations are at right angles to the direction of travel. With longitudinal waves the vibrations are in the same direction of travel.
|State what is meant by a radiation weighting factor.
|A measure of the biological effect of a radiation.
|Disposal of some types of radioactive waste from nuclear reactors is particularly difficult. Give a reason for this difficulty.
|Stays (highly) radioactive for a (very) long time
|Another student carries out the same experiment using a flask of larger volume. Explain why this is a better design for the experiment
|A flask of larger volume is better because this increases the mass and volume of air and used in the experiment. This should result in a smaller percentage error in the measurements of both mass and volume of the gas. This will in turn reduce the percentage error in the calculated density of air.
|Use the kinetic model to explain what happens to the pressure of trapped air if its volume increases.
|Pressure is caused by the gas particles exerting a force on the walls of the container. When the volume of the container decreases there is an increase in the collision rate, meaning that more force is exerted on the container walls. This increases the pressure as pressure is a measure of force per unit area (P = F/A).
|What change could be made to this circuit to ensure that the same capacitor stores more energy
|Increasing the supply voltage would increase the energy storing capacity of the capacitor. This is because the final voltage, across the fully charged capacitor, would be higher.
|In a laser the light is produced by stimulated emission of radiation. Explain the term 'stimulated emission' by making reference to the energy levels in atoms
|A high voltage or other energy source can be used to pump electrons up into higher energy states. For example, an electron can be pumped up to energy level (E2) and then fall into the metastable state E1, creating what is called an inverted population. A passing photon, having an energy equal to the energy gap E1 to E0 can encourage/stimulate an electron to drop from energy state E1 to E0 with the production of a photon in phase, with the same frequency and travelling parallel to the stimulating photon. Thereafter, photons produced by stimulated emission can cause further stimulated emission. This is the basis for stimulated emission and amplification.
|The distance between the screen and the laser is now doubled. State how the radius of the spot now compares with the one shown in the diagram. You must justify your answer
|The laser beam is non divergent. It does not spread out. This means the radius of the spot is a constant.
|Two 15kg masses, X and Y, shaped as shown, are dropped through the same distance on two identical uncovered concrete pipes. When the masses hit the pipes, the masses are brought to rest in the same time. Which mass causes more damage to a pipe? Explain your answer in terms of pressure
|Block X will cause more damage because the force, although the same for each block, is exerted over a smaller area. This results in more pressure applied to the pipe. Pressure = Force/Area
|In the circuit above, the 20 ohm resistor is now replaced with a 10 ohm resistor. The intensity of light is unchanged. The following measurements re obtained.S closed =0.011V. S open= 0.508V. Explain why the reading on the voltmeter, when S is closed is smaller than the corresponding reading in part (b)
|Decreasing the value of the load resistor will increase the current in the circuit. This will increase the "lost" volts (Vlost=Ir). Voltmeter reading = emf-Vlost This explains the lower reading on the voltmeter when the switch is closed.
|Explain why, as angle x is unchanged, it is important to keep the lightmeter at a constant distance from point X for each measurement of intensity.
|By keeping the light meter a constant distance from X you are justified in stating that any change in the recorded intensity is a result of changing q. If the distance was altered a change in intensity could be the result of a diverging beam.
|Explain what is meant by photoelectric emission from a metal.
|Photoelectric emission is the term used to describe the process by which an electron bound in an atom can absorb enough energy from a single photon to escape, or be emitted, from the atom.
|Explain why the actual temperature rise of the disc is less than
calculated in (b) (i).
|energy is lost to the surrounding air
|State which, if any, of the resistors will overheat
|30 ohm resistor will overheat
|The 9V d.c. supply is replaced by a 9V a.c. supply.
What effect, if any, would this have on your answers to part (b) (ii)?
|What energy change takes place in the microphone
|Sound energy to Electrical energy
|The amplifier processes the signal from the microphone.
What effect does the amplifier have on the signal’s
|Explain what is meant by the term “critical angle”.
|If light inside the prism strikes the surface at an angle greater than the critical angle it will be totally internally reflected.
|Explain how this circuit works to close the blind.
|The resistance of LDR drops
(with light level rise)
V across R rises
until MOSFET switches on the motor
|What is the purpose of the variable resistor R?
|to set the light level at which the blind closes.
|State whether or not the blinds will close when the light level is
|Since V< 2·4 V transistor will not switch on
so blinds do not shut.
|Why does each LED need a resistor in series?
|to limit current in/voltage across the LED
|What type of lens should be used?
|How would the shape of this lens have to be altered to give it a longer focal
|Make thinner/or less curved
|Name the eye defect which this type of lens could correct
|The radioactive source and detector are moved along the weld. How
would the count rate change when the detector moves over an air pocket?
Explain your answer.
|Count rate increases
Air is more easily penetrated/less metal to be penetrated
|Which of the radiations alpha, beta or gamma must be used?
Explain your answer.
|Gamma penetrates best/other two would not penetrate steel
|X-rays are sometimes used to detect air pockets.How does the wavelength of X-rays compare with gamma rays?
|x-rays longer/gamma shorter
|What is meant by the term “half-life”?
|time taken for half of the radioactive atoms to decay or activity to decrease by half
|Describe two precautions taken by the scientists to reduce the equivalentdose they receive while using radioactive sources
|Any 2 of shielding/limiting time of exposure/ increasing distance
|The risk of biological harm from radiation exposure depends on theabsorbed dose and the type of radiation. Which other factor affectsthe risk of biological harm?
|Speed at Q is greater, Mass of car is greater, Deceleration is less Since a = F/m (and F is constant) Can gain full marks by calculation
|Test repeated, same car but with passegers. Speed at P still 30 m s–1. Same braking force. How does the speed of the car at Q compare?
|What effect, if any, does this decrease in temperature have on the density of the oxygen in the cylinder?
both mass and volume remain
|Fewer molecules/atoms/particles inside canister so fewer collisions/hits with
walls per second
|Temp of oxygen inside cylinder remains constant. Explain, in terms of particles, why pressure of the gas inside the cylinder decreases.
|When in use, internal resistance of each cell gradually increases.
What effect, does this have on the power output of the heating
|Power output is less ½ Current is less RIP 2 = R (load) is constant
|State what is meant by the term capacitance.
|Quantity of charge stored per volt
|Yellow LED is lit _x000D_
Because it is forward biased
|Which LED(s) is/are lit at this value of output voltage?_x000D_
Justify your answer.
|State what is meant by an activity of 12 kBq.
|12000 decays per second
|State the average equivalent dose received by the hand on each
occasion. 0.030 μGy
|State whether the speed of ultrasound in brass is less than, equal to or greater than the speed of ultrasound in steel
|The speed of ultrasound is brass is less than it is in steel (1) AND it takes a longer time to travel the same distance (1)
|State what happens to the speed of the light as it enters a diamond
|It decreases/slows down
|State what is meant by the term half-life
|Time taken for activity to decrease by half OR time taken for half of the nuclei to decay
|State what is meant by a gamma ray
|An EM wave/a high frequency electromagnetic wave
|Describe the energy change that takes place as the marble (is dropped) and hits the sand
|kinetic energy to heat and sound energy
|Define the term acceleration.
|Acceleration is the change of velocity (not speed) in unit time
|Explain how the satellite can be accelerating when it is travelling at a constant speed.
|Direction of satellite is (continually) changing
|Gamma radiation is an example of radiation which causes ionisation. Explain what is meant by the term ionisation.
|Ionisation is when an atom gains or loses electrons
|The accepted value for the specific heat capacity of water is quoted in the table in the Data Sheet. Explain the difference between the accepted value and the value obtained in the experiment.
|Measured value of ܧ୦ too large OR Δ T too small
|How could the experiment be improved to reduce this difference?
|Which power supply should be used to operate the transformer?
|ac OR mains OR one on left
|What is the purpose of a transformer?
|Transformers are used to change* the magnitude † (size ok) of an (alternatin g) volta ge OR current
|What is the purpose of resistor R?
|To reduce current in LED
|State the energy change in a solar cell
|Light → electric (al) Not ‘electricity’
|Identify radiations P and Q.
|P – Ultraviolet OR UV,Q – Microwaves
|State what happens to the frequency of electromagnetic radiation as the wavelength increases.
|Carbon-14 emits beta particles. What is a beta particle?
|A radioactive source emits alpha particles. What is an alpha particle?
|A helium nucleus OR equivalent eg 2p + 2n
|How does the ionisation density of alpha particles compare with that of beta particles?
|Greater Stronger -0 More powerful -0
|One of the lamps now develops a fault and stops working. State the effect this has on the other lamp. You must justify your answer.
|The other lamp: remains lit, stays on, is the same brightness, gets brighter, is not affected. Justification: The current still has a path through the other lamp. (1)
The current in the other lamp is the same (only acceptable if other lamp stays same brightness) (1)
|Explain how the circuit operates to switch on the heater when the temperature falls below a certain value.
|(As Rth increases,) Vth increases (1)
(When Vth = 2·0 V or V reaches switching voltage,) MOSFET/transistor turns on (1)
Relay switches on (the heater). (1)
|The resistance of the variable resistor R is now increased. What effect does this have on the temperature at which the heater is switched on? You must justify your answer.
|Temperature decreases (1)
Resistance of thermistor must be greater / increase (1)
to switch on MOSFET / transistor (1)
|X-rays can cause ionisation. Explain what is meant by ionisation
|When an atom gains / loses / gains or loses electrons.
| The pilot and passengers are weighed before they board the helicopter. Explain the reason for this.
|To check that the maximum takeoff weight is not exceeded.
|The student launches the rocket a second time. For this launch, the student adds a greater volume of water than before. The same initial upward thrust acts on the rocket but it fails to reach the same height. Explain why the rocket fails to reach the same height.
|more water will increase weight/mass (1) unbalanced force decreases (1)
acceleration is less (1)
|3 x 10⁸ m/s