# Machines

## 45 terms · Topic 2: Machines

### Acceleration

If the velocity of something increase by 10m/s every second, then its acceleration is 10m/s²

### Big-Bang theory

The theory that the Universe was created when a single, incredible dense, hot 'superatom' expanded, more than 10 billion years ago

### Geostationary Orbit

An orbit specially chosen so that a satellite appears stationary in the sky. This is because it orbits at the same rate as the Earth turns

### Light Year

The distance travelled by light in one year. It is nearly 10000000000000km

### Moon

Large, rocky object that orbits a planet

### Orbit

Circular or elliptical path followed by an object as it moves around a planet, moon, or Sun

### Planet

Large object (such as the Earth) that orbits a star (such as the Sun)

### Star

A huge, hot glowing ball of gas, such as the Sun. It is powered by nuclear reactions

This is a star

### Universe

All the galaxies: everything that exists

### Ammeter

An instrument that measure current, in amperes (A)

### Ampere (A)

Unit of electric current

### Battery

A collection of electric cells - although the word is commonly used for a single cell as well

### Cell

A device that pushes current round a circuit when chemicals inside it react

### Charge

This is carried by some of the particles in atoms. There are two types: positive (+) and negative (-)

### Circuit Breaker

An electromagnetic switch that turns off the current in a circuit if this gets too high. It does the same job as a fuse but, unlike a fuse, can be reset

### Conductor (electrical)

A material that lets an electric current flow through it. Metals are the best conductors

### Current

A flow of charge. It is measured in amperes (A)

### Diode

A component that allows current to flow through it in one direction but not the other

### Direct Current (D.C)

Current which always flows in the same direction. The current from a battery is like this

### Efficiency

If an engine or motor has an efficiency of 0.25 (25%), only a quarter of the energy supplied to it is delivered as work. The rest is wasted

### Electron

A negatively (-) charged particle from the atom. In a circuit, the 'electricity' in the wires is a flow of electrons

### Energy

Things have energy if they can be used to do work - In other words, to make forces move. Energy is measured in joules (J)

### Force

A push or pull. It is measured in newtons (N)

### Friction

The force that opposes the motion of one material over another

### Fuse

A small piece of wire that overheats, melts, and breaks a circuit if the current gets too high

### Gravitational Field Strength

Near the Earth's surface, this is 10N/kg. In other words, there is a gravitational pull of 10N on each kg of mass

### Insulator (electrical)

A material that does not let an electric current flow through it.

Unit of mass

### Mass

The amount of matter in something it is measured in kilograms (kg)

### Metre (m)

Unit of length/1000m=1km

Unit of force

### Ohm (Ω)

Unit of electrical resistance

### Potential energy

The energy something has because of a change in position or shape

### Power

The rate at which an appliance transforms energy. It is measured in watts (W). 1W=1 J/S

### Resistance

This is measured in ohms. The higher the resistance of a conductor, the less current flows through it for each volt across it

Unit of time

### Speed

If something travels a distance of 10m in 1 second, its average speed is 10m/s

### Velocity

Speed in a particular direction. It is measured in m/s. An arrow, or a + or -, can be used to show its direction

### Voltage

The pressure that pushes electricity through wires in the same way that water pressure pushes water through pipes

Unit of voltage

### Voltmeter

An instrument that measured voltage, in volts (V)

### Watt (W)

Unit of power. It is equal to 1 joule per second

### Weight

The strength of the Earth's gravitational pull on an object. Being a force, it is measured in newtons (N)

### Work

Work is done whenever a force makes something move