Synoptic Exam Questions (Paper 1 & 2) (AQA A Level Physics): Exam Questions

The core of a thermal nuclear reactor contains a number of components that are exposed to moving neutrons. 

State what happens to a neutron that is incident on: 

• the moderator

• a control rod.

A slow-moving neutron collides with a nucleus of an atom of the fuel which induces nuclear fission. 

Describe what happens in the process of induced fission.

A student sets up the arrangement, shown in Figure 8, to demonstrate the principle of moderation in a nuclear reactor.

Figure 8

A golf ball of mass $m$ is initially hanging vertically and just touching a hockey ball of mass $3m$. The golf ball is pulled up to the side and released. After the collision, the balls move in opposite directions with equal speeds.

Explain, with numerical detail, how this arrangement demonstrates the moderation process in a reactor.

A thermal nuclear reactor produces radioactive waste.

State the main source of the most dangerous waste and describe one problem faced in dealing with the waste.

Thin films of carbon are sometimes used in electronic systems. 

Typical dimensions of such a film are shown in Figure 7.

Figure 7

Calculate the current which passes through the carbon film shown in Figure 7 for an applied voltage of 2.5 mV. 

The resistivity of carbon = 4.0 × 10^–5 Ω m

The applied voltage is kept constant, but the current is now directed through the carbon film as shown in Figure 8.

Figure 8

Show that the current is approximately 6 magnitudes larger when directed through the carbon film, as shown in Figure 8.

A tensile force is applied to the carbon film in Figure 8 in a plane that is normal to the current. 

Without performing any calculations, state and explain how the resistance of the carbon film changes as a result of the applied tensile force, stating one assumption you make.

The International Space Station (ISS) orbits travels around the Earth once every 93 minutes. 

Calculate the angular speed of the ISS.

Calculate the distance of the ISS above the Earth’s surface.

The Soyuz is a Russian spacecraft that carries astronauts to and from the international space station (ISS). The ISS has a mass of approximately 4.2 × 10⁵ kg. 

Calculate the change in kinetic energy of a Soyuz travelling from the Earth’s surface to the ISS.

Without performing any further calculations, explain how the change in kinetic energy relates to the change of the potential energy when the Soyuz travels from the Earth’s surface to the ISS. 

Cyclotrons are used to accelerate particles, such as protons, for a number of applications. 

A cyclotron has two D-shaped regions called ‘dees’ where the magnetic flux density is constant. The dees are separated by a small gap. An alternating electric field between the dees accelerates charged particles. The magnetic field causes the charged particles to follow a circular path. 

Figure 5 shows the path followed by a proton that starts from O.

 Figure 5

State the direction the magnetic field acts over the dees in Figure 5.

Explain why it is not possible for the magnetic field to alter the speed of a proton while it is in one of the dees.

Show that the time taken by a proton to travel around one semi-circular path is independent of the radius of the path.

The maximum radius of the path followed by the proton is 0.46 m and the magnetic flux density of the uniform field is 0.88 T. 

Calculate the maximum speed of a proton when it leaves the cyclotron. 

Ignore any relativistic effects.

The protons leave the cyclotron when the radius of their path is equal to the outer radius of the dees. 

Determine the radius required for the cyclotron to produce protons with a maximum kinetic energy of 25 MeV. 

Ignore any relativistic effects.

A student investigates the refraction of light using a semicircular glass block. The refractive index of the glass is 1.52.

State the two conditions required for total internal reflection to occur at a boundary.

A ray of light strikes the flat surface of the block at an angle of 50° to the normal, as shown in Figure 2.

Figure 2

Complete, on Figure 2, the path of the ray of light.

Support your answer with a suitable calculation.

The flat surface of the glass block is now placed in contact with water.

Explain how the student could use the glass block to measure the refractive index of water.

The student then uses a diffraction grating to analyse the light from a sodium lamp. The sodium lamp emits two closely spaced wavelengths known as the sodium doublet:

${\lambda }_1=589.0\text{ nm}{\lambda }_2=589.6\text{ nm}$

The diffraction grating has 600 lines per mm.

Calculate the angle of diffraction for the second-order maximum of ${\lambda }_1$.

The student wants to resolve the sodium doublet and is considering two options:

• Option 1: observe the second-order spectrum ($n=2$) using the original 600 lines per mm grating

• Option 2: observe the first-order spectrum ($n=1$) using a different grating with 1200 lines per mm

Discuss which option the student should choose.

Figure 4 shows part of a circuit used to detect temperature changes.

A fixed resistor of resistance $2.5\mathrm{\Omega }$ is connected in series with a thermistor of resistance $12\mathrm{\Omega }$ at room temperature. The battery has an emf of $6.0\mathrm{V}$ and an internal resistance of $0.50\mathrm{\Omega }$.

Figure 4

Calculate the current in the circuit.

Calculate the expected reading on the voltmeter.

The actual voltmeter reading is 4.6 V.

Suggest one reason for the difference between the expected and actual readings.

The fixed resistor is made from a wire of length $0.80\mathrm{m}$ and diameter $0.28\mathrm{mm}$.

Calculate the resistivity of the wire.

The thermistor is heated so that its resistance decreases to $3.0\mathrm{\Omega }$. A warning LED is to be connected in parallel with either the fixed resistor or the thermistor. The LED illuminates when the potential difference across it exceeds $2.0\mathrm{V}$.

Determine which component the LED should be connected across so that it acts as a high-temperature warning. Support your answer with calculations.

A turntable rotates at a constant angular speed. A small block of mass $0.050\mathrm{kg}$ is placed on the turntable at a distance of $0.12\mathrm{m}$ from the centre, as shown in Figure 6.

Figure 6

The block is on the verge of sliding when the turntable completes one revolution every $0.85\mathrm{s}$.

Calculate the angular speed of the turntable.

Show that the frictional force acting on the block is approximately $0.3\mathrm{N}$.

The block is now moved to a distance of $0.20\mathrm{m}$ from the centre. The turntable continues to rotate at the same angular speed. The maximum frictional force between the block and the turntable surface does not change.

Determine whether the block will slide at this new position.

The block is placed on a horizontal platform that is attached to a vertical spring, as shown in Figure 7. The platform oscillates vertically with simple harmonic motion. At a frequency of $2.5\mathrm{Hz}$, the mass just loses contact with the platform at the highest point of the oscillation when the amplitude is $0.040\mathrm{m}$.

Figure 7

Suggest the condition required for the mass to lose contact with the platform at the highest point.

Calculate the maximum amplitude at a frequency of $4.0\mathrm{Hz}$ for which the block remains in contact with the platform throughout the oscillation.

State what is meant by the internal energy of an ideal gas.

A sealed glass flask of volume $0.020{\text{ m}}^3$ contains air at $27°\mathrm{C}$. The pressure of air in the flask is $1.5\times {10}^5\text{ Pa}$.

Calculate the number of molecules of air in the flask.

Explain, using the kinetic theory model, why the pressure of an ideal gas increases when it is heated at constant volume.

The temperature of the air is increased from $27°\mathrm{C}$ to $127°\mathrm{C}$.

Calculate the change in the mean kinetic energy of a molecule of air in the flask.

When an ideal gas is heated at constant volume, all of the energy supplied by heating is used to increase the mean kinetic energy of the particles.

When air is heated at constant volume, its specific heat capacity is $720{\text{ J kg}}^{-1}{\text{ K}}^{-1}$.

Deduce whether air behaves as an ideal gas when heated at constant volume.

molar mass of air = $2.9\times {10}^{-2}{\text{kg mol}}^{-1}$

An isolated solid conducting sphere of radius $0.10\text{ m}$ is positively charged.

Figure 1 shows how the electric potential $V$ varies with distance $r$ from the centre of the sphere.

Figure 1

Determine the magnitude of the electric field strength at a distance of $0.20\text{ m}$ from the centre of the sphere.

State an appropriate SI unit for your answer.

The sphere acts as a capacitor because it stores charge at an electric potential.

Show that the capacitance of the sphere is approximately $1\times {10}^{-11}\text{ F}$.

The charged sphere momentarily touches an identical uncharged conducting sphere. The two spheres are then separated.

Explain why the total energy stored by the two spheres after separation is less than the energy stored by the single sphere before contact.