phy past paper Q

What is meant by elastic behaviour?

A material that has the ability to return to its original shape after the applied force is removed.

Give one reason why steel is a good material for a bar magnet.

Because it is a hard magnetic material which stays magnetized for a long time.

Explain how do we know that the magnetic field lines are uniform?

Field lines are evenly spaced and parallel to each other.

Give a reason why a voltage is induced between the ends of the metal wire when it moves between the poles.

Because the wire cuts through the magnetic field lines, which induces an EMF (voltage).

Two changes that would increase the magnitude of the induced voltage.

Move the wire faster / Use stronger magnets / Move the wire closer to the magnets

State one source of background radiation.

Food, the Sun, or cosmic rays

Describe how the teacher could measure the count rate from a radioactive source and correct for background radiation.

First, use a Geiger tube to take a reading without any radioactive source (background count). Then take a reading with the source. Subtract the background count from the second reading to get the count rate from the source only.

State the name of the wave behaviour responsible for the path of the ray of light as it passes into an optical fibre.

Total internal reflection

Explain the path of the ray of light as it travels through the optical fibre.

Total internal reflection occurs at every boundary because the glass core has a higher refractive index than the cladding, and the angle of incidence is greater than the critical angle.

Give a reason why a variable resistor is included in the circuit with an LED.

The variable resistor controls the current flowing through the LED. It can be adjusted to protect the LED or change its brightness.

Discuss the evolution of the stars Rigel and Sirius.

Both began as protostars in a nebula and are now main sequence stars. Rigel has a much higher mass than Sirius. Rigel will become a red supergiant and then explode as a supernova, while Sirius will become a red giant and then a white dwarf.

Name the wave that has a lower frequency than microwaves.

Radio waves

Explain why the temperatures of hot water and cold water change when mixed.

Heat energy flows from the hot water to the cold water by conduction until both reach the same temperature (thermal equilibrium).

Explain how placing a lid on a plastic cup would affect the cooling of hot water.

The lid prevents heat loss by convection, so the water cools more slowly and reaches equilibrium at a higher temperature over a longer time.

Give the name of another object that can orbit the Earth.

A satellite (natural or artificial)

Give a difference between the orbit of a planet and the orbit of a comet.

Comets have highly elliptical (oval-shaped) orbits, while planets have nearly circular orbits.

Which type of radiation is a high energy electron?

Beta particles (beta-minus radiation)

Give a thermal effect of infrared waves.

Infrared waves heat surfaces, such as skin or objects, by causing molecules to vibrate.

Two similar properties of visible light and infrared waves.

1. Both are electromagnetic waves. 2. Both travel at the speed of light in a vacuum.

Two differences between visible light and infrared waves.

1. Infrared has a longer wavelength. 2. Visible light has a higher frequency.

Give the property that determines whether a star becomes a red giant or a supergiant.

Mass (more massive stars become supergiants; less massive stars become red giants)

Discuss the difference between a red giant and a white dwarf.

A red giant is much larger, cooler on the surface, and still undergoing fusion. A white dwarf is very small, dense, and hot, but no longer undergoes fusion.

Explain the advantages of using domestic electricity with parallel circuits.

Each lamp can be controlled independently because each lamp is on its own branch. If one lamp fails, the others stay on.

What is voltage?

Voltage is the energy transferred per unit charge (joules per coulomb).

Explain why a plastic bottle collapses when air is removed from inside.

The air pressure outside the bottle becomes greater than the pressure inside, so the outside force crushes the bottle.

Describe the differences between the orbit of the Moon and the orbit of a comet.

The Moon orbits a planet (Earth) in a nearly circular path. A comet orbits a star (the Sun) in a highly elliptical (oval) path.

State one harmful effect of microwaves.

Microwaves can cause internal heating of body tissues, leading to burns or other damage.

Describe how energy is transferred by conduction through a metal strip.

When one end of the metal strip is heated, particles vibrate faster and pass these vibrations to neighbouring particles, transferring thermal energy along the strip.

State how a student could improve the reliability of their experiment results.

Repeat the experiment several times, remove any anomalous results, and calculate the mean average.

Give the name of a fuel that could be used in a nuclear reactor.

Uranium-235 (or plutonium-239)

Describe the process of nuclear fission inside a reactor.

A uranium-235 nucleus absorbs a neutron and splits into two smaller daughter nuclei, releasing energy and 2-3 more neutrons. These neutrons go on to split other uranium nuclei, creating a chain reaction.

Explain how electricity is generated by a generator.

A coil of wire rotates inside a magnetic field. The wires cut through the magnetic field lines, which induces a voltage. If the circuit is complete, current flows.

Suggest how the output voltage of a generator could be reduced.

Spin the coil more slowly, use weaker magnets, or use fewer turns of wire on the coil.

Describe the difference between alternating current (AC) and direct current (DC).

AC constantly reverses direction. DC flows in only one direction.

Describe the energy transfer when a student lifts a marble and drops it to point B.

Chemical potential energy in the student's muscles transfers mechanically to gravitational potential energy in the marble. When dropped, gravitational potential energy transfers mechanically to kinetic energy. Some energy also transfers to thermal energy (heats the marble and surroundings).

Describe a method a student could use to measure the speed of a rolling marble.

Mark a start line and a finish line a measured distance apart. Use a stopwatch to time how long the marble takes to roll between the lines. Calculate speed using speed = distance ÷ time. Repeat and take an average.

Which three statements about the electromagnetic spectrum are correct?

1. All electromagnetic waves travel at the same speed in free space (3 × 10^8 m/s). 2. Radio waves have the longest wavelength in the electromagnetic spectrum. 3. All electromagnetic waves transfer energy.

Is "all electromagnetic waves are longitudinal" true or false?

False. Electromagnetic waves are transverse, not longitudinal.

Is "X-rays have the highest frequency in the electromagnetic spectrum" true or false?

False. Gamma rays have the highest frequency. X-rays have the second highest.

Is "all electromagnetic waves can cause cancer" true or false?

False. Only high-frequency waves (UV, X-rays, gamma rays) can cause cancer. Radio waves and microwaves do not have enough energy.

Give one use and one harmful effect of microwaves.

Use: heating food. Harmful effect: can cause internal heating of body tissue.

Give one use and one harmful effect of gamma rays.

Use: sterilising medical equipment (by killing microbes). Harmful effect: increased risk of cancer (due to its ionising effect — can damage/mutate/kill cells).

Which of these also orbits the Earth? A) a comet B) Mars C) the Moon D) the Sun

C) the Moon

Which of these forces causes the ISS to orbit the Earth? A) air resistance B) electrostatic C) friction D) gravitational

D) gravitational

Which of these substances is not attracted to a bar magnet? A) cobalt B) copper C) iron D) nickel

B) copper

State two changes that could be made that would decrease the magnitude of the force on the wire.

1. Lower current. 2. Weaker magnets.

Discuss the differences in the frequency of sound heard by the driver of a moving car compared to a person standing at the side of the road.

The driver hears a higher frequency because the sound waves are compressed (wavefronts get closer together) as the car moves forward. The person at the side of the road hears a lower frequency as the car moves away because the wavefronts are stretched apart. This is the Doppler effect. The speed of sound remains constant.

Give an advantage of using a circuit breaker instead of a fuse.

It can be reset. A fuse has to be replaced.

Suggest a reason why the heater may switch off before it reaches its normal operating current.

It might have a fuse in its plug that is lower than a specific amps. The fuse would blow first.

What is the correct life cycle order of the Sun?

Nebula → main sequence → red giant → white dwarf

Which stages occur in the life cycle of the Sun?

Nebula, main sequence, red giant, white dwarf

Does a black hole occur in the life cycle of the Sun?

No

Does a neutron star occur in the life cycle of the Sun?

No

Does a red supergiant occur in the life cycle of the Sun?

No

Does a supernova occur in the life cycle of the Sun?

No

What stage comes after the red giant in the Sun's life cycle?

White dwarf

What stage comes before the main sequence in the Sun's life cycle?

Nebula

Explain the difference between the Sun and Betelgeuse, based on the different colours of their surfaces.

Betelgeuse is red, which means its surface is cooler than the Sun. The Sun is yellow, so its surface temperature is higher than Betelgeuse's.

Give a reason why energy is not transferred from the Sun to the Earth by conduction or convection.

Conduction and convection require matter/particles. There is no matter/particles in space (it is a vacuum).

A satellite orbiting the Earth contains sensitive equipment that can be damaged if it gets too hot. Explain which colour would be most appropriate for the outer surface of the satellite to protect the equipment.

A shiny, light-coloured surface (e.g., white or silver) to reflect heat/infrared radiation. Shiny (white/silver) surfaces are good reflectors and poor absorbers of infrared radiation.

Describe a method to accurately determine the mass and volume of each rock.

Measure mass using a balance (zeroed, level, dry rock). Measure volume using water displacement in a measuring cylinder (subtract initial water level from final water level after submerging rock).

State what is meant by the term half-life.

The average time taken for the activity to halve, or for half the radioactive nuclei to decay.