IGCSE Combined Science Physics

Brownian motion

Motion of small particles suspended in a liquid or gas caused by molecular bombardment

thermal expansion

An increase in the volume of a material when the temperature is increased

Infrared radiation

Electromagnetic waves with wavelengths that are longer than visible light but shorter than microwaves.

Wave motion

the transfer of energy without transferring matter

real image

An upside-down image formed where rays of light meet.

conventional current

Current that flows from the positive side of the battery to the negative side. This is the way current is drawn in circuit diagrams, even though it is wrong.

Ampere

unit of electric current

D.C. supply

Density formula

mass/volume

Gravitational Potential Energy formula

m x g x change in h

power unit

Watts (W)

Speed unit

m/s (meters per second)

Acceleration unit

m/s^2

boiling

The temperature at which a liquid changes to a gas

Solidifying

liquid to solid

longitudinal wave

a wave in which the particles of the medium vibrate parallel to the direction of wave motion

Refraction

the change in direction of a ray or wave when it passes from one medium to another

angle of incidence

the angle between the incident ray and the normal

angle of refraction

the angle between the refracted ray and the normal

converging lens (convex)

a lens that bends exiting light rays toward the focal point

inverted

upside down

Current

Rate at which electric charge passes a point in a circut

Battery

Voltmeter

Closed switch

Weight formula

mass x gravity

Acceleration formula

final velocity-initial velocity/time

speed formula

distance/time

Force formula

mass x acceleration

Pressure formula

force/area

kinetic energy formula

1/2mv^2

Work formula

force x distance

Power formula

work/time

Work & Energy unit

Joules (J)

Force unit

N (newtons)

Pressure unit

Pascal (Pa)

States of matter

solid, liquid, gas

melting

The change in state from a solid to a liquid

Evaporation

The change of a substance from a liquid to a gas

Condensing

The change of state from a gas to a liquid

Atom

Smallest particle of an element

Molecule

two or more atoms held together by chemical bonds

Attractive forces

the force by which one object attracts another, fixed position in solid and close together in a liquid

melting point

The temperature at which a solid becomes a liquid

boiling point

The temperature at which a liquid changes to a gas

thermal conduction

the transfer of thermal energy from one substance to another through vibration of molecules

thermal conductor

a substance that conducts thermal energy well

thermal insulator

a substance that conducts thermal energy poorly

Convection

The transfer of thermal energy through a material by the movement of the material

convection current

The transfer of thermal energy by the motion of a fluid

electromagnetic spectrum

All of the frequencies or wavelengths of electromagnetic radiation

crest

Highest point of a wave

trough

Lowest point of a wave

Wavelength

Horizontal distance between the crests or between the troughs of two adjacent waves

Amplitude

For a wave, the maximum displacement on either side of the equilibrium (midpoint) position.

Frequency

the number of complete wavelengths that pass a point in a second

Hertz (Hz)

Unit of measurement for frequency

transverse wave

A wave that moves the medium in a direction perpendicular to the direction in which the wave travels

wave speed=

frequency x wavelength

Reflection

the change in direction of a ray or wave when it strikes a surface without passing through it

angle of reflection

The angle between the reflected ray and the normal

normal

the line drawn at right angles to a surface at the point where a ray hits the surface

ray diagram

a diagram showing rays that can be drawn to determine the size and location of an image formed by a mirror or lens

plane mirror

a mirror with a flat surface

incident ray

The Ray that strikes a surface

reflected ray

The Ray that is reflected from a surface

virtual image

a reflected optical image (as seen in a plane mirror)

focal length

the distance from the center of a lens to the focal point/principal focus

principal focus or focal point

the point at which rays of light parallel to the principal axis converge after passing through a converging lens

spectrum

waves, or colours, separated out in order according to their wavelengths

Dispersion

the separation of different wavelengths of light because they are refracted through different angles

ultrasound

Sound waves with frequencies above 20,000 Hz.

Positive charge

Type of electrical charge carried in nucleus of an atom

Negative charge

Type of electrical charge carried in electrons

Direct Current (DC)

Electric current that flows in only one direction

Alternating Current (AC)

A flow of electric charge that regularly reverses its direction.

Ammeter

A device used to measure current in a circuit

Current=

charge/time

volt (V)

unit for measuring voltage

electrical force (e.m.f.)

Voltage across the terminals of a source or the electrical work done by a source (cell, battery, etc)

potential difference (p.d.)

the work per unit charge from electrical energy into other energy forms by a device

resistance=

Potential difference/current

ohm

unit of electrical resistance

Energy transferred=

current x p.d. x time

power=

current x potential difference

voltmeter

a device used to measure p.d. (voltage) between 2 points

charge=

current x time

Lamp

LED

Fuse

LDR

Ammeter

Motor

Fixed Resistor

Variable resistor

Open Switch

A.C. supply

Earth/Ground

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