Grade 9 Physical Sciences: Forces, Electricity, and the National Grid

Vocabulary practice flashcards covering contact and non-contact forces, gravity, mass and weight, magnetic and electrostatic interactions, the national power grid, electrical safety devices, and circuit fundamentals.

Motion

The change in position of an object over time, characterized by a change in speed and/or a change in direction.

Contact Forces

Forces that come into play when objects physically touch or interact with each other, such as friction, applied force, tension, and normal force.

Non-contact Forces

Forces that act on objects from a distance without direct physical contact, such as gravitational force, magnetic force, electrostatic force, and nuclear force.

Applied Force

A force exerted on an object by a person or another object.

Air Resistance Force

A frictional force caused by the presence of air that acts in the opposite direction to the motion of an object moving through the air.

Normal Force

The supporting force exerted by a surface pushing against an object placed on it, which prevents the object from falling through the surface.

Tension Force

The force transmitted through a rope, string, cable, chain, or wire when it is pulled by opposing forces acting on either end.

Frictional Force

The force that resists motion when the surface of one object comes into contact with and attempts to move relative to the surface of another.

Resultant Force (Net Force)

The vector sum of all the individual forces acting on an object, representing the overall combined effect on the object.

Vector

A physical quantity, such as force, that possesses both a magnitude (size or length) and a direction (represented by an arrow).

Newton ($\text{N}$)

The standard SI unit in which force is measured, named after Sir Isaac Newton.

Gravitational Force

The non-contact attraction (pull) force between any two objects due to their masses.

Gravitational Acceleration ($g$)

The acceleration experienced by an object falling freely towards a celestial body due to gravity, equal to approximately $9.8\,\text{m}\cdot\text{s}^{-2}$ near the surface of the Earth.

Mass

The quantity or amount of matter that makes up an object, measured in grams ($\text{g}$) or kilograms ($\text{kg}$), which remains constant regardless of location.

Weight ($w$)

The downward gravitational force exerted on an object by a celestial body (such as Earth), measured in newtons ($\text{N}$) and calculated using $w = m \times g$.

Permanent Magnet

A magnet that retains its magnetic properties over an extended period of time, typically made of alloys containing iron, nickel, or cobalt.

Temporary Magnet

A magnetic material, such as soft iron, that becomes magnetized easily but loses its magnetism quickly.

Electromagnet

A temporary magnet created by wrapping insulated wire around an iron or steel core and passing an electric current through it, losing its magnetism when the current is turned off.

Magnetic Field

A region of space surrounding a magnet where magnetic forces are exerted on other magnetic objects or moving charges, visualized with field lines directed from the North pole to the South pole.

Electrostatic Force

A non-contact force exerted between electrically charged objects over a distance, where like charges repel each other and unlike charges attract each other.

Triboelectric Charging

The process of charging materials through friction when rubbed together, causing the physical transfer of electrons from one object to another.

Conduction (Electrostatics)

The transfer or sharing of electrons between objects that occurs when a charged object comes into direct physical contact with a neutral object.

Polarisation (Electrostatics)

The temporary shifting of charges within a neutral object when a charged object is brought near without touching, making one side temporarily positive and the opposite side temporarily negative.

Nuclear Force

A strong attractive force that acts between nucleons (protons and neutrons) inside an atomic nucleus, holding it together against the electrostatic repulsion of protons.

Eskom

The state-owned power utility company in South Africa responsible for electricity generation, high-voltage transmission, and distribution to consumers.

National Electricity Grid

An interconnected network of power stations, step-up/step-down transformers, transmission lines, substations, and distribution lines that delivers electricity across the country.

Hydro-electricity

Renewable electricity generated by utilizing the kinetic energy of falling or flowing water (such as from dams or waterfalls) to spin turbines connected to generators.

Solar Energy

Renewable energy captured from the sun, where radiant and heat energy is converted directly into electrical energy using solar panels and stored in batteries.

Nuclear Fission

The splitting of a heavy atomic nucleus (such as uranium or plutonium) into smaller fragments when hit by a neutron, releasing large quantities of heat and radiation.

Nuclear Fusion

A nuclear process where two light atomic nuclei combine to form a heavier nucleus, releasing vast amounts of energy and powering stars like the Sun.

Live Wire

The brown-insulated conductor inside a three-pin plug that delivers electrical current from the power supply into the appliance.

Neutral Wire

The blue-insulated conductor inside a three-pin plug that completes the circuit by carrying current back to the supply.

Earth Wire

The green-and-yellow striped safety wire in a three-pin plug that grounds an appliance, channeling fault current safely into the ground to protect users from electric shock.

Fuse

A safety device containing a thin wire designed to melt and open an electrical circuit when the current exceeds a predetermined safe limit.

Circuit Breaker

A resettable electrical safety switch that uses an internal electromagnet to automatically trip and break the circuit whenever an excessive current flows.

Lightning Conductor

A pointed metal rod placed atop a high structure and connected by a thick copper conductor to the earth, safely capturing and dissipating lightning strikes.

Electric Current ($I$)

The rate of flow of electric charge (electrons) past a point in a circuit, measured in amperes ($\text{A}$) using an ammeter connected in series.

Potential Difference (Voltage, $V$)

The difference in electrical potential energy between two points in a circuit, measured in volts ($\text{V}$) using a voltmeter connected in parallel.

Electrical Resistance ($R$)

The opposition offered by a conductor or device against the flow of electrical charge, measured in ohms ($\Omega$) according to Ohm's relation $R = \frac{V}{I}$.

Series Circuit

An electrical circuit configuration containing only one conductive pathway for current, where current is identical through all components and total voltage is divided.

Parallel Circuit

An electrical circuit configuration containing multiple independent pathways, where total current divides among branches and potential difference is equal across each branch.

Conventional Current

The standard conceptual flow of electric charge from the positive terminal of a power source, through the external circuit, to the negative terminal.