Definitions Flashcards
Electromotive Force
Energy transferred per unit charge from chemical to electrical form.
Resistance
Potential difference across a component/current in it.
Kilowatt — Hour
(A unit of) energy equal to 3.6MJ or 1kW for an hour.
The Ohm
A component with a resistance of 1(ohm) if a potential difference of 1V makes a current of 1A to flow through it.
Potential Difference
Energy transferred per unit charge from electrical to other forms.
Coulomb
Unit of charge. The amount of charge that passes in 1s when the current is 1A.
Power
Work done/energy transferred per unit time.
The Volt
1J per coulomb. The potential difference is 1V when 1J of energy is used to pass 1C of charge through a component.
Resistivity
Resistivity = Resistance x Cross Sectional Area / Length
Kirchoff’s First Law
The total current into a junction equals the total current out. Conservation of charge.
Kirchoff’s Second Law
The sum of EMF’s = the total p.d around a (closed) loop (in a circuit). Energy is conserved.
Displacement
The distance moved from equilibrium from a part on a wave.
Amplitude
The maximum displacement (caused by wave motion).
Wavelength
Distance between (neighbouring) identical points on a wave of the same phase.
Period
Time taken for one complete oscillation.
Phase Difference
Between two points on the same wave/waves of the same frequency, how far through the cycle one point is to another.
Frequency
The number of wavelengths passing a point at a point per unit time or produced by the wave source.
Speed of a Wave
Distance travelled by the wave (energy) per unit time.
Nodes
A node occurs where the amplitude/displacement is (always) zero.
Antinodes
An antibode occurs where the amplitude (of the standing wave) takes the maximum (possible) value.
Fundamental Mode of Vibrations
The lowest natural frequency of a standing wave.
Harmonics
Whole number multiples of the fundamental frequency of a stationary wave.
Interference
When (two) waves meet (at a point) there is a change in overall intensity/displacement.
