Physics Paper 3 June 2023

1. ARandom errors scatter the readings on either side of the true value and are reduced by averaging, while a systematic error shifts every reading the same way and is not.
2. BRandom errors shift every reading by the same amount in the same direction, while a systematic error scatters the readings on either side of the true value.
3. CRandom errors and systematic errors both scatter the readings on either side of the true value, and averaging enough readings removes each of them.
4. DRandom errors affect only the last digit of a reading, while a systematic error changes the size of the physical quantity that is being measured.

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1. AElectric charge and gravitational potential, since each of them is defined as a quantity taken per unit mass or per unit charge.
2. BMagnetic flux density and electric field strength, since each is defined as a force per unit quantity acting in a stated direction.
3. CGravitational potential and decay constant, since each of them describes how a property changes with position or with time.
4. DElectric charge and decay constant, since each of them may be given either a positive or a negative sign within a calculation.

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1. AAir resistance acts on the object throughout the fall and does negative work on it, so it gains less speed.
2. BThe horizontal velocity of the object is lost during the fall, so only the vertical component is left at the ground.
3. CThe acceleration of free fall falls off with height, so the object accelerates rather less than the calculation assumes.
4. DThe object is given an upward push as it leaves the aeroplane, and this cancels part of its downward velocity.

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1. AIt rises, because the water from the melted ice adds its whole volume to the water that was already in the beaker.
2. BIt falls, because water is denser than ice, so the melted ice occupies a smaller volume than the solid block occupied.
3. CIt rises, because the block no longer pushes any water aside once the whole of it has turned into liquid water.
4. DIt stays the same, because the melted ice has exactly the volume of water that the floating block was displacing.

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1. AThe satellite is losing energy steadily to friction with the upper atmosphere, so its total energy falls further below zero as the orbit decays.
2. BThe satellite travels round the planet in the opposite sense to the planet's own rotation, so its total energy is counted in the negative direction.
3. CThe kinetic energy of the satellite is itself negative, because the satellite is moving against the direction of the gravitational force acting on it.
4. DThe satellite is bound to the planet: energy has to be supplied to it to move it out of the field to infinity, where the energy is zero.

1. AA sound of constant loudness whose pitch rises and falls as the detector moves from one end of the line to the other.
2. BA single loud point at the middle of the line, with silence at every other position along the line the detector follows.
3. CA sound that grows steadily louder as the detector approaches the midpoint of the line and then fades away again.
4. DA regular succession of loud and quiet points, loud where the path difference is a whole number of wavelengths.

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1. AIncrease the power delivered to the single loudspeaker so that the sound that it emits becomes very much louder.
2. BMove the single loudspeaker steadily back and forth while the detector is being moved along the line in front of it.
3. CPlace a barrier with two narrow, closely spaced gaps in front of the single loudspeaker.
4. DConnect the single loudspeaker to a second signal generator running at a slightly different frequency from the first.

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1. AA wave travelling along the string and its reflection from a fixed end, of equal frequency and opposite direction, superpose.
2. BA single wave travels along the string and slows down at the fixed ends, so its crests bunch together into a fixed pattern.
3. CTwo waves of slightly different frequency travel along the string in the same direction and beat against one another.
4. DThe string is driven at one end so hard that each part of it vibrates quite independently of the parts on either side.

1. AA stationary wave transfers energy faster than a progressive wave, because two waves rather than one are contributing to it.
2. BA stationary wave transfers no energy along its length, whereas a progressive wave carries energy in its direction of travel.
3. CA stationary wave carries energy in both directions at once, whereas a progressive wave carries energy in one direction only.
4. DA stationary wave transfers energy only at the nodes, whereas a progressive wave transfers energy only at each of its crests.

1. AThe width of the blurred border that appears around the outline of every structure recorded in the image.
2. BThe smallest separation of two structures that can still be seen as two separate structures in the finished image.
3. CThe difference in the degree of blackening between the parts of the image formed by adjacent structures.
4. DThe total intensity of the X-ray beam that reaches the film after passing through the patient being examined.

1. AMake the area of the anode struck by the electrons as small as possible, so the source is nearly a point.
2. BPlace a lead grid between the patient and the film so that scattered X-rays are absorbed before reaching it.
3. CRaise the accelerating voltage of the tube so that the X-rays that are produced become much more penetrating.
4. DGive the patient a barium meal so that the soft tissue absorbs a larger fraction of the beam passing through it.

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1. AThe maximum value the voltage reaches in either direction during one cycle.
2. BThe value of the alternating voltage averaged over one complete cycle of the supply.
3. CThe steady direct voltage that would deliver the same mean power to a given resistor.
4. DThe difference between the highest and the lowest voltage reached during one cycle.

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1. AThe operational amplifier supplies extra current from its own power supply into the divider, so the p.d. across the 10 kilohm resistor rises.
2. BThe meter reads correctly in both cases; it is the divider that behaves differently, because the supply is loaded more heavily in one arrangement.
3. CThe meter's resistance is small compared with the divider, so used directly it draws current and lowers the p.d.; the follower takes none.
4. DThe operational amplifier amplifies the p.d. across the 10 kilohm resistor by a factor of seven, so the buffered reading is the larger of the two.

1. AThe e.m.f. of 1 V induced in a coil of a single turn when the flux threading it changes by 1 Wb in each second.
2. BThe magnetic flux passing through an area of 1 m squared placed at right angles to a field of unit strength.
3. CThe flux density that gives a force of 1 N on each metre of a wire carrying 1 A at right angles to the field.
4. DThe force of 1 N acting on a charge of 1 C moving at 1 m per second along the direction of the magnetic field.

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1. AThe capacitor blocks direct current completely, so no charge at all is able to reach either of its plates while the switch stays closed.
2. BThe alternating supply has a mean voltage of zero over a cycle, so it is never able to drive any charge at all on to the plates.
3. CThe supply reverses each half cycle, so the capacitor charges one way then discharges and charges the other way, holding no steady charge.
4. DThe capacitor charges to the peak voltage almost at once and then leaks all of that charge away again through the internal resistance.

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1. AThe internal energy of a system is increased both by the heat supplied to it and by the work done on it.
2. BIf two bodies are each in thermal equilibrium with a third body, they are in thermal equilibrium with each other.
3. CEnergy cannot be created or destroyed by any process, but only changed from one form into another form.
4. DHeat flows of its own accord from a body at a higher temperature to a body at a lower temperature.

1. AIt does not depend on the properties of any particular substance, being fixed by absolute zero and the triple point of water.
2. BIt is measured in kelvin rather than in degrees celsius, the two scales being in every other respect identical to one another.
3. CIt can be used only for temperatures above the triple point of water, whereas an empirical scale carries no such restriction.
4. DIt assumes that a chosen thermometric property changes linearly between the two fixed points that are chosen for the scale.

1. ABy compressing the system quickly while keeping it perfectly insulated from its surroundings throughout the process.
2. BBy allowing heat to flow out of it to cooler surroundings, or by letting it do work as it expands.
3. CBy raising the temperature of the surroundings so that they hold the system at one fixed temperature throughout.
4. DBy adding more of the same substance to the system while holding both its pressure and its volume constant.

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1. AThe temperature of the air is the same as the temperature of the metal body of the car.
2. BThe air inside the car is completely dry, so that it contains no water vapour of any kind at all.
3. CThe molecules of the air lose no energy at all when they collide with the inside walls of the car.
4. DThe air behaves as an ideal gas over the range of pressure and temperature involved.

1. AThe area of the loop between the two curves is energy per unit volume put in but not recovered, and it stays in the rubber.
2. BThe molecules of the rubber are forced closer together as it is stretched, and the work done in compressing them raises its temperature.
3. CAir resistance acts on the band each time it is moved quickly, and the work done against that resistance is converted into internal energy.
4. DThe rubber is a poor conductor of heat, so the energy produced in the athlete's hands cannot escape and builds up within the band.

1. AOne whose density and whose viscosity both increase steadily and smoothly with the depth below the surface.
2. BOne that obeys the gas laws exactly at every pressure and at every temperature to which it is subjected.
3. COne in which the molecules exert no forces at all on one another except during collisions between them.
4. DOne that is incompressible and has no viscosity, and whose flow is steady and streamline throughout.

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1. AIt passes through undeflected as well, since the selected speed does not depend on the charge of the particle.
2. BIt slows down until the two forces acting on it balance, and then passes through the selector undeflected.
3. CThe magnetic force on it exceeds the electric force, so it is deflected aside and stopped by the slit.
4. DThe electric force on it exceeds the magnetic force, so it is pulled forward and leaves the beam faster.

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1. ABright lines on a bright background, formed when white light is passed through a gas hotter than the source producing it.
2. BDark lines on a continuous bright background, formed when a cool gas absorbs photons of its own characteristic energies.
3. CBright lines on a dark background, formed when the excited atoms of a gas fall back to their lower energy levels.
4. DDark lines on a dark background, formed when the atoms of a cool gas emit photons of their own characteristic energies.

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1. AThe fraction of the nuclei present in the source that have already decayed since it was first made.
2. BThe probability that any one nucleus in the source will decay during the next one second of time.
3. CThe energy carried away each second by the particles and the radiation that the source is emitting.
4. DThe number of nuclei in the source that disintegrate in each unit of time.

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1. AAn AM signal occupies a much narrower bandwidth, so many more stations fit into a given part of the spectrum.
2. BAn AM signal is far less affected by electrical noise, since noise mostly alters the amplitude of a radio wave.
3. CAn AM broadcast carries a wider range of audio frequencies, so the quality of the sound that is reproduced is higher.
4. DAn AM signal can be received by any aerial without a tuned circuit, since it has no side bands of its own.

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1. AThe signal is reproduced over a greater distance, since each sample is transmitted with more power behind it.
2. BThe reconstructed signal follows the original waveform more closely, but more bits are produced each second.
3. CFewer bits are produced each second, so the signal can be transmitted over a channel of much smaller bandwidth.
4. DThe amplitude of each sample is measured more precisely, so the number of quantisation levels available is greater.