VCE Physics Unit 3/4 Edrolo Glossary

Charge

a scalar property of matter that can cause it to experience a force in an electromagnetic field (electric or magnetic). Types may only be positive or negative (an arbitrary naming convention).

uncharged object

has a net zero, or equal, amount of positive and negative charge within it. This may also be called neutral.

charged object

has a net amount of either positive or negative charge within it.

Positive charges

Charges which attract negative charges and repel positive charges.

Negative charges

Charges which attract positive charges and repel negative charges.

Coulomb's law

The magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.

electrical permittivity

a measure of the resistance offered by the substance in creating an electric field within it and affects the transmission of the electrical force. A material that is easily polarised has a high permittivity. The SI unit for permittivity is farad⋅m−1

electric field

a vector field that associates to each point in space the Coulomb force that would be experienced per unit of electric charge, by an infinitesimal test charge at that point

electric field strength

the magnitude of the force per unit charge on an infinitesimal positive test charge placed in the field

Properties of electric field lines

1. They begin on positive charges and end on negative charges.

2. They never cross (at any given point there is only one value for the electric field).

3. They indicate electric field direction by a tangent to the field lines.

4. Where field lines are:

a. closely spaced, the field is strong

b. the field is distantly spaced the field is weak

c. parallel and equally spaced, the field is uniform.

Electric potential

defined as the electrical potential energy per unit charge at a particular point in an electric field. Has has a value of V=W/q, where W is the work done by some force external to the field to bring a small test charge q from infinity to a particular point in an electric field. Electric potential is zero at infinity. Electric potential is a scalar, and all points in an electric field have an electric potential. Each point has only one scalar value for electric potential.

Potential difference

the difference of electric potentials taken at two different points.

equipotentials

When the potential difference between two points is zero. No work is done in moving between equipotentials.

electron-volt

the amount of energy needed to move an electron through a potential difference of one volt.

electric current

a flow of electric charge defined as the rate of flow of charge past a given cross-section of material or space

charge carriers.

particles that move, and that have a charge

conductor

a material that allows mobile charge carriers within it to move with a significant net translational motion when an electrical potential difference is applied across the material. The mobile charge carriers in a material may be negative or positive (or there may be both).

Conventional current

arbitrarily defined as the direction in which positive charges flow.

Connecting conductors

Circuit elements which are assumed to be made from metals that do not dissipate electric energy as charge passes through them.

electric cell

A circuit element which increases the electric potential energy of any charge that flows through it

Resistors

materials that impede (resist) internal charge flow and that transform electrical potential energy into some other form such as internal thermal energy.

Kirchhoff's first law

the net current entering and leaving a junction is zero

Kirchhoff's second law

in traversing any closed loop in a circuit the net electric potential difference must be zero

absorption spectrum

the specific set of frequencies of light that a material absorbs due to electron energy transitions

AC (alternating current) electricity

electricity with a periodically alternating direction of current and voltage

acceleration

the rate of change of velocity per unit time (vector quantity)

accuracy

a relative indicator of how well a measurement agrees with the 'true' value of a measurement

air resistance

the force of air particles resisting the motion of objects through the air. Also known as the drag force in air

alternator

a device that transforms kinetic energy into AC electricity by electromagnetic induction; an AC generator

amplitude (waves)

the magnitude of a particle's maximum displacement from its neutral point within a wave.

angle of incidence (waves)

the angle to the normal of a ray approaching a medium boundary

angle of reflection (waves)

the angle to the normal of a ray reflected by a medium boundary

angle of refraction (waves)

the angle to the normal of a ray refracted by a medium boundary

antinode

a point where constructive interference consistently occurs

aperture

a hole, gap, or slit through which a wave travels

bar magnet

a permanent magnet in the shape of a prism

centripetal force

the net force causing circular motion which is always directed towards the centre of a body's circular path

charge

a quantifiable property which relates to how strongly an object is affected by an electric field

coherence

a property of two wave sources when they create waves of the same frequency in the same medium

coherent light

a beam of light with a consistent frequency and phase

collision

the coming together of two or more objects where each object exerts a force on the other

compression (longitudinal wave)

a point in the medium of a longitudinal wave where pressure is a maximum

compression (spring)

the process of decreasing an object's length

compression wave

see longitudinal wave

conical pendulum

a mass on the end of a string which undergoes horizontal circular motion

connected bodies

two or more objects either in direct contact or attached by a string, rope, or cable

contracted length (special relativity)

the length of an object measured in a reference frame where the object is moving; this length is always shorter than the proper length

controlled variable

a variable that has been held constant in an experiment in order to test the relationship between the independent and dependent variables

conventional current

current that is assumed to consist of flowing positive charges so that the direction of current is the direction a positive charge would move

crest

a point in the medium of a wave where particles have maximum positive displacement

critical angle (waves)

the angle above which total internal reflection occurs

current (electric)

the rate of flow of electric charge

curve of best fit

a curved line that indicates the relationship between the independent and dependent variables on a graph. It must pass through the uncertainty bars of all data points

DC (direct current) electricity

electricity with a constant direction of current and voltage

de Broglie wavelength

the wavelength associated with a particle due to its momentum

dependent variable

a variable that the experimenter measures, which is predicted to be affected by the independent variable. Dependent variables are plotted on the vertical axis of graphs

design speed

the speed on a banked track for which there is no sideways frictional force acting on the vehicle

diffraction

the spread of a wave around an obstacle or through an aperture

dilated time

the time interval between two events measured in a reference frame where the two events occur at different points in space; this time is always greater than the proper time between the events

dipole

a source (field lines point away) and a sink (field lines point towards) paired together

discrete

limited to certain values (not continuous)

displacement

the change in position of an object (vector quantity)

distance

the total length of a given path between two points (scalar quantity)

Doppler effect

the detected frequency change due to the relative motion between a wave source and detector

elastic collision

a collision in which kinetic energy is conserved

electric field strength

a measure of the electric force that acts per unit of charge at a point in space

electromagnet

a magnet created by an electric current

electromagnetic induction

the production of an electromotive force (EMF) due to the change in magnetic flux through a conducting loop

electromagnetic spectrum

the range of all electromagnetic waves ordered by frequency and wavelength

electromagnetic wave

waves that consist of perpendicular electric and magnetic field oscillations

electromotive force (EMF)

the voltage created or supplied due to energy being transformed into electrical potential energy

electron-volt

a measure of energy equal to 1.6x10^-19 J, derived from the loss or gain of energy by an electron moving across a potential difference of 1 volt

emission spectrum

the specific set of frequencies of light that a material emits due to electron energy transitions

energy

a scalar quantity describing the ability to cause a physical change

energy dissipation

the transfer of energy out of a system

equilibrium

the state of having all the forces acting on an object in balance which means the net force on the object is zero

equilibrium position (spring-mass system)

the position of the mass at which the net force on the mass is zero. This position is always halfway between the two extreme points (endpoints) in oscillatory motion

error

the difference between a measured value and its 'true' value

event

something that occurs at a particular location and time

extension

the process of increasing an object's length

field (model for non-contact forces)

a region of space in which each point is subject to a non-contact force

force

a push or a pull with an associated magnitude and direction (vector quantity)

forced oscillation

the oscillation caused by the periodic application of an external driving force

frame of reference

a set of coordinates by which we measure the relative location and motion of objects

frequency

the number of cycles completed per unit of time

friction

a force that resists the relative motion of two surfaces which are in contact

fringe spacing

the distance between adjacent bright or dark bands in a double slit interference pattern

fundamental force

a force that cannot be broken down into other forces

fundamental frequency

the lowest frequency of a standing wave in a given medium

fusion

see nuclear fusion

generator

a device that transforms kinetic energy into (either AC or DC) electricity by electromagnetic induction

gradient

the graphical representation of the rate of change of one variable with respect to another

gravitational field strength

a measure of the gravitational force that acts on each unit of mass at a point in space

gravitational force

the force experienced by an object due to the gravitational field of another object

gravitational potential energy

the stored energy associated with the position of an object in a gravitational field

harmonic

a standing wave with a frequency equal to an integer multiple of the fundamental frequency

human error

see personal error

hypothesis

a proposed explanation that predicts a relationship between variables and can be tested through experimentation

ideal spring

a spring that obeys Hooke's law so that the force it exerts is proportional to its change in length

impulse

a vector quantity equal to the change in momentum of a body as the result of a force acting over a time