OCR A Level Physics A Exploring Physics June 2024 question paper H556/02

Which one of these non‑invasive medical scans does not expose the patient to ionising radiation?

A CAT

B PET

C Ultrasound

D X‑ray

Your answer

The image shows a display of an oscilloscope which is measuring an alternating voltage. The time base is set at 0.1 s / division. The voltage scale (y‑sensitivity) is set at 0.5 V / division.

Which row of the table shows the correct amplitude and correct frequency?

Your answer

A student is using a spreadsheet to model the decay of charge on a capacitor. They are using the equation = – The student chooses a time interval of 0.5 s. At time t = 0.0 s the charge on the capacitor is 600 C.

Part of the modelling spreadsheet is shown below.

What is the charge on the capacitor at t = 1.5 s?

A 130 C

B 240 C

C 246 C

D 307 C

Your answer

The diagram shows a string stretched between two posts.

The string is plucked and a stationary wave is set up.

What is the phase difference between P and Q?

A 0 rad

D rad

Your answer

What is the radius of a carbon nucleus that has 6 protons and 7 neutrons?

Assume that the average radius of a nucleon r₀ is 1.2 fm.

A 2.2 fm

B 2.3 fm

C 2.8 fm

D 1.6 fm

Your answer

A sub‑atomic particle has a positive charge.

Which type of particle is it?

A anti‑proton

B down quark

C neutrino

D positron

Your answer

A 1.0 k resistor is connected in series to a battery made of three 1.2 V cells connected as shown. The cells have negligible internal resistance.

What is the reading on the ammeter?

A 1.2 mA

B 1.8 mA

C 2.4 mA

D 3.6 mA

Your answer

Thermistors are circuit components whose resistance varies with temperature.

There are two major types; negative temperature coefficient (NTC) thermistors, whose resistance decreases with increasing temperature and positive temperature coefficient (PTC) thermistors, whose resistance increases with increasing temperature.

A student is investigating how the resistance of a thermistor varies with temperature by measuring current and voltage. The thermistor is placed in a water bath and the temperature of the water measured using a thermometer.

The diagram below shows how the student set up the experiment (water bath not shown). The circuit has been set up incorrectly.

Describe how the student should change the circuit.

The circuit was corrected and then used to collect data.

The table shows data collected from the investigation.

Temperature / C	Current / mA	Voltage / V
30	0.75	3.00
40	1.10	3.00
50	1.51	3.00
60	2.10	3.00
70	2.80	3.00
80	3.66	3.00
90	4.76	3.00

The axes below show a plot of current against temperature. The first four points from the table have been plotted. Plot the remaining points.

Draw a suitable line of best fit through the data points.

Describe, using the graph and calculations using data from the table, how the resistance of the thermistor varies for increasing temperature. Hence determine whether the thermistor the student used was an NTC or a PTC thermistor.

The thermistor is used in a temperature‑sensing circuit for a heating system to warm milk for a baby.

The student considers two possible designs for the circuit which are shown below.

In each circuit, the voltage V_out across the thermistor is connected to the heating system for warming the milk.

Discuss which circuit may be suitable for the heating system by considering the response of the circuit to changes in temperature.

Explain these observations.

The distance between the centres of X and Y is 70.0 cm, the distance D (as shown in the diagram) is 4.00 m and the distance from P₁ to P₂ is 1.25 m.

Use the two source interference formula to calculate the frequency of the sound waves. (Speed of sound = 340 m s^–1)

Loudspeaker Y is now replaced with a loudspeaker that produces sound waves of twice the original amplitude.

Describe how the signal observed on the oscilloscope varies as the microphone is moved along the line P₁ to P₃.

Explain what is meant by the term intensity.

Calculate the factor by which the intensity of the sound waves at P₁ in (c) is larger than the intensity of the original sound waves at P₁.

18* (a) Describe how an experiment can be conducted to determine how the output current of a step‑up transformer depends on the number of turns on the secondary coil.

Explain how the data collected can be analysed to establish the relationship between the output current and the number of turns on the secondary coil.

You are provided with wire and a suitable core on which to wind the wire, as well as any other normal laboratory equipment.

Use the space below to draw a labelled circuit diagram.

State Faraday’s law.

Show that the number of turns on the secondary coil is 20.

At one particular instant, the output voltage from the transformer is 3.4 V.

Calculate the change in magnetic flux experienced by the secondary coil in a short time interval of 1.2 ms and state its unit.

Assume that the output voltage from the transformer remains constant at 3.4 V over this time interval.

Show that each X‑ray photon produces about 2000 light photons.

The photocathode has a work function of 2.3 eV.

Explain what is meant by the work function.

Calculate the maximum kinetic energy of the electrons leaving the photocathode.

12 X‑ray photons are detected every minute.

Use your answer to (a) to calculate the current I leaving the photocathode. Assume that all the photons of light produce photoelectrons.

State one other assumption you have made to enable you to calculate the current I in (b)(iii).

Explain what is meant by nuclear binding energy of a nucleus.

Explain why isotopes with low mass numbers, such as hydrogen, are those which undergo nuclear fusion.

Use the diagram given at the start of this question to show that, for the reaction of deuterium and tritium, the energy released in each fusion event is approximately 3 × 10^–12 J.

Determine the charge of the missing particle.

The missing particle is a lepton. Name this lepton.

In the fusion reaction above, determine the total number of up quarks at the start of the reaction.

Explain what is meant by a tracer.

A technetium‑99m tracer with an activity of 900 MBq is injected into a body. The half‑life of technetium‑99m is 6.01 hours.

Calculate the number of technetium‑99m nuclei initially present in the tracer.

Calculate the time in hours taken for the activity of the tracer to have fallen to 3.0% of its initial activity.

This question is about lightning.

Sheet lightning occurs when there is an electrical discharge between the upper and lower regions of a thunder cloud. The upper regions are positive and the lower regions are negative.

The thunder cloud can be modelled as an ideal parallel plate capacitor with circular horizontal plates.

The data for the capacitor comes from the cloud.

The diagram shows the plates of the model capacitor superimposed on the cloud.

Draw on the diagram to show the electric field lines between capacitor plates.

Suggest why the actual electric field lines of the cloud would differ from what you have drawn.

Calculate the capacitance C of the model capacitor.

Assume the permittivity of the material of the cloud is the same as the permittivity of free space.

Calculate the magnitude of the charge Q on one of the plates of the model capacitor.

Fork lightning is an electrical discharge that occurs between the bottom of the cloud and the surface of the Earth.

Another cloud has a charge of 155 C and is at a height of 2.0 km.

The surface of the Earth has an electrical potential V of 0 V.

Assume the cloud acts as a point charge.

Calculate the magnitude of the electrical potential V between the cloud and the surface of the Earth.

A fork lightning strike has a duration of 25 ms. The cloud discharges at a constant rate. The cloud is uncharged after the strike.

Calculate the number of electrons reaching the ground in 1.0 ms.