Grade 9 Natural Sciences – Term 3 Key Vocabulary

These flashcards cover essential Grade 9 Natural Sciences terminology from Term 3, including forces, gravitation, magnetism, electricity, circuits, safety, and energy generation.

Force

A push or pull that occurs when two objects interact.

Newton (N)

The SI unit used to measure force.

Contact Force

A force that requires two objects to touch, e.g., pushing a chair.

Field (Non-contact) Force

A force acting at a distance without touching, e.g., gravity or magnetism.

Friction

The force that resists motion between surfaces rubbing together.

Tension

A pulling force that stretches an object.

Compression

A pushing force that squashes or shortens an object.

Gravitational Force

The field force that pulls matter together.

Weight

The gravitational force the Earth exerts on an object; measured in newtons (N).

Mass

The amount of matter in an object; measured in kilograms (kg).

Weight Formula (W = m × g)

Weight equals mass multiplied by gravitational acceleration (9.8 m·s⁻² on Earth).

Magnetic North

The planet’s magnetic pole to which a compass needle points.

True North

The geographic (rotational) North Pole of Earth.

Opposite Magnetic Poles

Attract each other.

Like Magnetic Poles

Repel each other.

Electric Cell

A device that produces electricity through chemical reactions.

Volt (V)

The unit of potential difference (energy per charge) a cell can supply.

Battery

Two or more cells connected together to provide electrical energy.

Series Connection (Cells)

Cells joined end-to-end; voltages add to give higher output.

Parallel Connection (Cells)

Cells joined side-by-side; voltage stays the same, current capacity increases, cells last longer.

Current

The rate at which charge flows through a circuit point; measured in amperes (A).

Ampere (A)

The SI unit of electric current.

Resistance

The opposition a material offers to electric current; measured in ohms (Ω).

Ohm (Ω)

The SI unit of resistance.

Resistor

A component designed to limit or control current, often converting electrical energy to heat or light.

Potential Difference (Voltage)

Energy supplied per coulomb of charge; measured with a voltmeter.

V = I × R

Ohm’s law: potential difference equals current times resistance.

Series Circuit

Circuit with a single current path; current is the same everywhere, voltage divides across components.

Parallel Circuit

Circuit with multiple paths; voltage is the same across branches, current divides inversely to resistance.

Transformer

Device that steps voltage up or down in the national grid.

National Grid

Network of power stations, transformers, substations and lines distributing electricity country-wide.

Grid Overload

When electricity demand exceeds supply.

Load Shedding

Intentional power cuts to certain areas to prevent grid overload.

Power Surge

Sudden rise in supply voltage that can damage electronics.

Surge Protector

Device that shields appliances from power surges.

Live Wire (Brown)

Carries current to an appliance.

Neutral Wire (Blue)

Returns current from the appliance to the supply.

Earth Wire (Green/Yellow)

Safety wire directing fault current safely to the ground.

Earth-Leakage Circuit Breaker (ELCB)

Device that cuts the main supply when a leakage current is detected.

Overloaded Connection

Too many appliances on one outlet causing overheating and possible fire.

Illegal Connection

Unauthorized link to the power grid lacking safety features; risk of electrocution and fire.

Renewable Energy Source

Energy that is naturally replenished, e.g., wind, water, sunlight.

Thermal Power Station

Generates electricity by burning fossil fuels to create steam that turns turbines.

Hydro-electric Power Station

Uses falling or flowing water to spin turbines for electricity generation.

Wind Power Station

Employs wind-driven rotor blades connected to generators.

Tidal Power Station

Harnesses rising and falling tides through turbines to make electricity.

Solar Power Station

Uses the sun’s energy (heat or light) to generate electricity.

Nuclear Fission

Splitting atomic nuclei (usually uranium) to release energy in nuclear reactors.

Radioactive

Emitting harmful ionizing radiation; characteristic of certain nuclear materials and waste.