GCSE Physics Syllabus

State Ohm's law equation relating potential difference, current and resistance.

$$V = IR$$ where $V$ is potential difference (V), $I$ is current (A), and $R$ is resistance (Ω).

Define resistance and give its unit.

Resistance is the opposition to the flow of electric charge, equal to potential difference divided by current. Its unit is the ohm (Ω).

In a series circuit, how do current, potential difference and resistance behave?

Current is the same everywhere; potential difference is shared between components ($V_{total}=V_1+V_2+\dots$); total resistance is the sum of resistances ($R_{total}=R_1+R_2+\dots$).

In a parallel circuit, how do current and potential difference behave?

The potential difference across each branch is the same; the total current is the sum of the currents through the branches ($I_{total}=I_1+I_2+\dots$).

Why is the total resistance of two resistors in parallel less than either resistor alone?

Adding a parallel branch provides an additional path for the current, so more current flows for the same potential difference, meaning the total resistance decreases.

State the two equations for electrical power.

$$P = VI \qquad P = I^{2}R$$ where $P$ is power (W), $V$ is potential difference (V), $I$ is current (A), and $R$ is resistance (Ω).

State the equation linking energy transferred, power and time.

$$E = Pt$$ where $E$ is energy (J), $P$ is power (W), and $t$ is time (s).

State the equation for energy transferred by an electrical circuit using charge and potential difference.

$$E = QV$$ where $E$ is energy (J), $Q$ is charge (C), and $V$ is potential difference (V).

Define power.

The rate of energy transfer (or the rate of doing work): $$P = \frac{E}{t} = \frac{W}{t}$$ measured in watts (W), where 1 W = 1 J/s.

State the equation for density, defining each symbol and unit.

$$\rho = \frac{m}{V}$$ where $\rho$ is density (kg/m³), $m$ is mass (kg), and $V$ is volume (m³).

Define density.

The mass per unit volume of a substance — how much mass is contained in a given volume.

Compare the density and particle arrangement of solids, liquids and gases.

Solids: particles packed closely in fixed positions, highest density. Liquids: particles close but able to move, slightly lower density. Gases: particles far apart and random, much lower density.

Name the changes of state and the transitions they represent.

Melting (solid→liquid), freezing (liquid→solid), boiling/evaporating (liquid→gas), condensing (gas→liquid), and sublimation (solid→gas).

Why are changes of state described as physical rather than chemical changes?

No new substance is made; the material recovers its original properties if the change is reversed, and its mass is conserved.

Define specific latent heat.

The energy required to change the state of 1 kg of a substance with no change in temperature.

State the equation for the energy needed for a change of state.

$$E = mL$$ where $E$ is energy (J), $m$ is mass (kg), and $L$ is the specific latent heat (J/kg).

What is the difference between specific latent heat of fusion and of vaporisation?

Fusion is the energy to change between solid and liquid; vaporisation is the energy to change between liquid and gas (vaporisation is usually the larger value).

Define the internal energy of a system.

The total kinetic energy and potential energy of all the particles (atoms and molecules) that make up the system.

What happens to the internal energy of a substance when it is heated?

The internal energy increases, which either raises the temperature (increasing particle kinetic energy) or produces a change of state (increasing particle potential energy).

Why does temperature stay constant during a change of state despite continued heating?

The supplied energy is used to break bonds between particles (increasing potential energy) rather than to increase their kinetic energy, so temperature does not rise.

What is the difference between a contact and a non-contact force? Give an example of each.

A contact force acts only when objects physically touch (e.g. friction, air resistance, tension, normal reaction). A non-contact force acts at a distance (e.g. gravity, magnetic, electrostatic force).

State the equation for weight, defining each symbol.

$$W = mg$$ where $W$ is weight (N), $m$ is mass (kg), and $g$ is gravitational field strength (N/kg, about 9.8 N/kg on Earth).

Distinguish between mass and weight.

Mass is the amount of matter in an object (kg) and is constant; weight is the force of gravity on the object (N) and varies with gravitational field strength.

Define a scalar and a vector quantity, giving one example of each.

A scalar has magnitude only (e.g. speed, mass). A vector has both magnitude and direction (e.g. velocity, force).

State the equation for the pressure a fluid exerts due to its depth (column of liquid).

$$p = h\rho g$$ where $p$ is pressure (Pa), $h$ is depth (m), $\rho$ is density (kg/m³), and $g$ is gravitational field strength (N/kg).

State the general equation defining pressure in terms of force and area.

$$p = \frac{F}{A}$$ where $p$ is pressure (Pa), $F$ is force normal to the surface (N), and $A$ is area (m²).

Why does the pressure in a liquid increase with depth?

There is a greater weight of liquid above a point at greater depth, so a larger force acts over the same area, increasing the pressure.

Explain what causes upthrust on an object submerged in a fluid.

Pressure increases with depth, so the upward pressure on the bottom of the object is greater than the downward pressure on the top, producing a net upward force (upthrust).

State the condition for an object to float in a fluid.

The object floats when the upthrust equals its weight; this occurs when the object's density is less than (or equal to) the density of the fluid.

Define the moment of a force and state its equation.

The moment is the turning effect of a force about a pivot: $$M = Fd$$ where $M$ is the moment (Nm), $F$ is the force (N), and $d$ is the perpendicular distance from the pivot to the line of action of the force (m).

State the principle of moments for an object in equilibrium.

For a balanced object, the total clockwise moment about a pivot equals the total anticlockwise moment about that same pivot.

How do levers and gears make it easier to do work?

A lever acts as a force multiplier: a force applied far from the pivot produces a larger force nearer the pivot. Gears transmit rotational effects: a larger gear driven by a smaller one turns with a greater moment (more force) but more slowly.