IGCSE Physics 0625/13 May/June 2025 Past Paper with Answers

Question 1

A pendulum is set swinging. The total time for $20$ complete swings is measured as $30\ \text{s}$. What is the time for one complete swing of the pendulum?

1. $1.5\ \text{s}$
2. $0.67\ \text{s}$
3. $0.75\ \text{s}$
4. $3.0\ \text{s}$

Question 2

Which piece of laboratory apparatus is used to measure the volume of an irregularly shaped solid by water displacement?

1. measuring cylinder
2. balance scale
3. metre ruler
4. lab thermometer

Question 3

A speed against time graph is plotted for the motion of a car. Which quantity is represented by the area enclosed between a speed-time curve and the time axis?

1. distance travelled by the car
2. acceleration of the car
3. average speed of the car
4. final velocity of the car

Question 4 · Answer A

Step 1: Weight is the gravitational force on an object; it is measured in newtons, the SI unit of force. Step 2: Density (kg/m^3), mass (kg) and volume (m^3) are not forces.

Question 5 · Answer A

Step 1: Density = mass / volume. P: $15/30 = 0.50\ \text{g/cm}^3$. Q: $25/30 \approx 0.83\ \text{g/cm}^3$. R: $35/30 \approx 1.17\ \text{g/cm}^3$. S: $45/30 = 1.50\ \text{g/cm}^3$. Step 2: An object floats if its density is less than the liquid's $0.95\ \text{g/cm}^3$. Step 3: P (0.50) and Q (0.83) are less than 0.95, so P and Q float.

Question 6 · Answer A

Step 1: Constant speed in a straight line means zero acceleration. Step 2: Newton's second law: $F = ma$, so zero acceleration means zero resultant force. Step 3: Therefore there is no resultant force on the car.

Question 7 · Answer A

Step 1: Moment $M = F \times d$, so $F = M/d$. Step 2: Convert $600\ \text{mm} = 0.60\ \text{m}$. Step 3: $F = 50 / 0.60 \approx 83\ \text{N}$.

Question 8 · Answer A

Step 1: Work done is force multiplied by the distance moved in the direction of the force. Step 2: $W = F d$ gives joules (newtons multiplied by metres).

Question 9 · Answer A

Step 1: Coal is burned in a boiler to heat water and produce high-pressure steam, which drives a turbine. Step 2: Tides, water in a dam (hydroelectric), and wind do not require boilers - they drive turbines directly using moving water or air.

Question 10 · Answer A

Step 1: Solid to liquid is melting; liquid to solid would be freezing. Step 2: Liquid to gas is boiling; gas to liquid would be condensing. Step 3: So the two changes are melting then boiling.

Question 11 · Answer A

Step 1: In a liquid, particles touch each other and almost no space lies between them. Step 2: In a gas, particles are far apart with large empty spaces between them. Step 3: Pushing the gas reduces those spaces, so the gas compresses. The liquid's particles are already touching, so it cannot be compressed.

Question 12 · Answer A

Step 1: Pressure depends on how often (and how hard) particles strike the walls. Step 2: Constant temperature means the particles' average speed stays the same. Step 3: In a larger volume, each particle has more space and reaches the wall less often per second, so the pressure drops.

Question 13 · Answer A

Step 1: Heating a solid makes it expand: its volume rises. Step 2: A higher volume with the same mass means a lower density. The hole in the nut and the length of the iron rod also grow. Step 3: Mass depends only on the amount of matter, which is unchanged when heating, so the mass of the coin stays the same.

Question 14 · Answer A

Step 1: Energy from the hot water reaches the hand through the glass wall by conduction. Step 2: Glass is a poor thermal conductor, so the energy travels slowly through it, giving a delay before the hand feels warm.

Question 15 · Answer A

Step 1: Heating makes the liquid expand: the same mass now fills a larger volume. Step 2: Density = mass / volume, so density falls. Step 3: The less dense warm liquid rises while cooler, denser liquid sinks, forming a convection current.

Question 16 · Answer A

Step 1: With no air gap, the pan touches the hotplate, so the main route is conduction through the contact surface. Step 2: Metals are excellent thermal conductors, so the metal hotplate moves energy into the pan very effectively by conduction.

Question 17 · Answer A

Step 1: Frequency $f = 12 / 180 = 1/15\ \text{Hz} \approx 0.0667\ \text{Hz}$. Step 2: Wavelength $\lambda = 10\ \text{m}$. Step 3: Wave speed $v = f\lambda = 0.0667 \times 10 = 0.67\ \text{m/s}$.

Question 18 · Answer A

Step 1: Sound waves are longitudinal: the air particles vibrate along the direction the sound travels. Step 2: A pulse sent along a stretched spring (a slinky) where coils compress and stretch in the direction of travel is also longitudinal. Step 3: Water waves and a transverse rope pulse have vibrations at right angles to the direction of travel - they are transverse, not longitudinal.

Question 19 · Answer A

Step 1: Air to glass: light slows down and bends towards the normal. Step 2: Glass to air: light speeds up and bends away from the normal. Step 3: Because the two glass faces are parallel, the bending at each face cancels in direction, so the emergent ray is parallel to the original incident ray (but shifted sideways).

Question 20 · Answer A

Step 1: Use the thin lens equation $\frac{1}{f} = \frac{1}{u} + \frac{1}{v}$. Step 2: $\frac{1}{f} = \frac{1}{15} + \frac{1}{30} = \frac{2}{30} + \frac{1}{30} = \frac{3}{30} = \frac{1}{10}$. Step 3: Therefore $f = 10\ \text{cm}$.

Question 21 · Answer A

Step 1: A typical TV remote uses a small LED on its front that emits infrared light. Step 2: Gamma rays, ultraviolet and X-rays are too high in energy and would be dangerous, expensive, or impossible to generate from a tiny battery.

Question 22 · Answer A

Step 1: The higher the frequency of an EM wave, the more energy each photon carries. Step 2: Ultraviolet, X-rays and gamma rays carry enough energy to ionise atoms and damage cells. Step 3: Visible light and radio waves do not normally damage cells - so the harmful pair here is gamma rays and ultraviolet.

Question 23 · Answer A

Step 1: The human audible range is conventionally given as $20\ \text{Hz}$ to $20\,000\ \text{Hz}$. Step 2: Ultrasound is defined as sound with frequency greater than $20\,000\ \text{Hz}$. Step 3: So the scale labels frequencies in hertz.

Question 24 · Answer A

Step 1: Repulsion is the only definite test for a magnet, because magnets repel only other magnets. Step 2: Block 2 shows repulsion, so block 2 must itself be a magnet. Step 3: Block 1 is only attracted, which any soft-magnetic material (such as iron) will show; so block 1 is not necessarily a magnet.

Question 25 · Answer A

Step 1: Only electrons (negative charges) can move during rubbing - protons stay in the nucleus. Step 2: The glass rod becomes positive, which means it has lost negative charge. Step 3: So electrons have moved from the glass rod to the silk cloth.

Question 26 · Answer A

Step 1: In a metal, the outer electrons are free to move; they carry the current. Step 2: When a potential difference is applied across the wire, these electrons drift slowly along its length. Step 3: Positive ions in the lattice stay in fixed positions, only vibrating slightly.

Question 27 · Answer A

Step 1: Both e.m.f. and potential difference are measured in volts. Step 2: Current is measured in amperes "electromotive force (e.m.f.) and potential difference (p.d.)" and charge in coulombs "potential difference (p.d.) and current", so they differ. Step 3: Resistance is measured in ohms ($\Omega$), which is different from volts.

Question 28 · Answer A

Step 1: $R = V / I$. Step 2: $R = 10 / 0.050 = 200\ \Omega$.

Question 29 · Answer A

Step 1: Heating a thermistor lowers its resistance. Step 2: Total resistance in the series circuit falls, so the current increases (ammeter rises). Step 3: Voltmeter reads $V = IR$ across the fixed resistor; $R$ is unchanged but $I$ rises, so the voltmeter reading also rises.

Question 30 · Answer A

Step 1: Two $3.0\ \Omega$ resistors in series give $R_\text{total} = 6.0\ \Omega$. Step 2: Current $I = V / R = 12 / 6.0 = 2.0\ \text{A}$.

Question 31 · Answer A

Step 1: Operating current $I = P / V = 2700 / 240 = 11.25\ \text{A}$. Step 2: A fuse must be rated above the normal current but as low as practical. Step 3: $3\ \text{A}$, $5\ \text{A}$ and $10\ \text{A}$ would all blow when the vacuum cleaner runs; the next standard rating above $11.25\ \text{A}$ is $13\ \text{A}$.

Question 32 · Answer A

Step 1: Output voltage ($20\ \text{V}$) is less than input ($240\ \text{V}$), so the transformer steps voltage down. Step 2: Turns ratio: $\frac{N_p}{N_s} = \frac{V_p}{V_s}$, so $N_p = N_s \times \frac{V_p}{V_s} = 600 \times \frac{240}{20} = 600 \times 12 = 7200$.

Question 33 · Answer A

Step 1: A negative ion has more electrons than protons. Step 2: To make it neutral, the extra electrons must be removed; the ion has to lose electrons.

Question 34 · Answer A

Step 1: The top number is the mass number $A = 15$ (total nucleons). Step 2: The bottom number is the proton number $Z = 7$. Step 3: Neutrons $N = A - Z = 15 - 7 = 8$.

Question 35 · Answer A

Step 1: Natural sources of background radiation include rocks and building materials, food, drink, the human body, and radon gas from the ground; cosmic rays from space are also natural. Step 2: Nuclear power stations and mobile phones are man-made and are not natural background radiation. Step 3: Only one list has zero man-made entries.

Question 36 · Answer A

Step 1: Alpha particles are heavy and doubly charged, so they ionise atoms strongly over a short range. Step 2: Gamma rays (not beta) are the most penetrating and they are electromagnetic waves. Step 3: Beta particles are fast electrons; they are particles, not part of the EM spectrum.

Question 37 · Answer A

Step 1: Lead is a dense metal whose atoms absorb the energy of nuclear radiation, especially gamma rays. Step 2: Radiation cannot be neutralised, repelled or dissolved - only absorbed.

Question 38 · Answer A

Step 1: One day equals one full spin of the Earth on its axis, so the day and night cycle is caused by Earth's rotation. Step 2: Seasons arise because the Earth's tilted axis points the same way through a full orbit of the Sun; the cycle period equals the orbital period (1 year). Step 3: Moon orbits the Earth in about 1 month and gives us lunar phases, not seasons.

Question 39 · Answer A

Step 1: A larger planet mass gives a stronger gravitational field at the surface. Step 2: Gravitational field strength falls as the distance from the planet grows.

Question 40 · Answer A

Step 1: The Sun's spectrum peaks in the visible, with significant amounts in the infrared (the warmth we feel) and the ultraviolet (which causes sunburn). Step 2: Microwaves, radio waves and X-rays make up much smaller portions of the Sun's emission.