Module 4 Flashcards
Electric Current
Rate of flow of charged particles
Conventional Current
A model used to describe the net movement of charge in a circuit. Conventional current flows from the positive to the negative terminal.
Conservation of Charge
Charge is conserved in all interactions: it cannot be created or destroyed.
Coulomb
One coulomb of electric charge passes a point in one second when there is an electric current of one ampere flowing.
Amp
The current flowing in two parallel wires separated by one metre in a vacuum such that there is an attractive force of 2.0 x 10^-7 N per metre length of wire between them.
Electrolyte
A fluid that contains ions that are free to move, act as charge carriers and hence conduct electricity.
Number Density
The number of free (delocalised) electrons per unit volume of material.
Conductor
A material with a high number density of conduction electrons and therefore a low resistance.
Insulator
Amaterial with a small number density of conduction electrons and therefore a very high resistance.
Semiconductor
A material with a lower number density of conduction electrons than a conductor and therefore a higher resistance.
Mean Drift Velocity
The average displacement of electrons moving along a wire per unit time.
Electromotive force
EMF is the energy transferred per unit charge when chemical energy is converted into electrical energy.
Potential Difference
Potential difference is the energy transferred per unit charge when electrical energy is converted into another form of energy.
Volt
Where one joule of energy is transferred when one coulomb of charge passes from one point to the other.
Resistance
The resistance of a conductor is the ratio of the pd across it to the current flowing through it.
Ohm
P.D. Of 1V
Currents of 1A
Ohm’s Law
For a conductor at constant temperature, the current flowing through the conductor is directly proportional to the pd across its ends.
Kilowatt-hour
For a conductor at constant temperature, the current flowing through the conductor is directly proportional to the pd across its ends.
Kirchoff’s First Law
The sum of the currents entering any point in an electrical circuit is equal to the sum of the currents leaving that point, as charge is conserved.
Kirchoff’s Second Law
The sum of the emfs around any closed loop in a circuit is equal to the sum of the pds around the same closed loop, as energy is conserved.
Internal Resistance
Some energy is transformed into thermal energy within the cell; it behaves as if it had a resistance.
Resistivity
The material’s resistance multiplied by its cross-sectional area divided by its length.
Progressive Wave
A wave which transfers energy from one point to another without a transfer of matter.
Longitudinal Wave
A wave where the oscillations of the particles are parallel to the direction of travel of the wave.
Transverse Wave
A wave where the oscillations of the particles are perpendicular to the direction of travel of the wave.
Displacement (wave)
The distance of a point on the wave from the equilibrium position.
Amplitude
The maximum displacement of any point on the wave from the equilibrium position.
Wavelength
The distance from any point on the wave to the next subsequent point in phase.
Wave Speed
The speed at which energy is transferred by the wave.
Frequency (wave)
The number of oscillations at a point per unit time.
Time Period
The time taken for one complete oscillation.
Phase Difference
How far ‘out of step’ the oscillations at two points on the same wave are.
Diffraction
The spreading out of a wave after passing through a gap or past an obstacle.
Plane Polarisation
Plane polarised waves have oscillations in one plane only, which is perpendicular to the direction of propagation.
Intensity
The rate of energy incident per unit area.
Refreactive Index
Amaterial property equal to the ratio between the speed of light in a vacuum and the speed of light in that given medium.
Critical Angle
The angle of incidence that results in the refracted ray travelling along the media boundary. (angle of refraction = 90°)
Interference
When two or more coherent waves superpose at a point, there is a change in overall displacement.
Principle of Superposition
When two waves interfere at a point, the resultant displacement is the sum of the individual displacements.
Path Difference
The extra distance travelled by one of the waves compared with the other.
Coherent Waves
Waves which have a constant phase difference.
Node
A point where the amplitude of oscillations is always zero.
Antinode
A point where the amplitude of oscillations takes the maximum possible value.
The Photoelectric Effect
The emission of electrons from a metal surface when photons are incident on that surface.
Photon
A quantum of energy of electromagnetic radiation.
Electronvolt
The energy gained by an electron which is accelerated through a pd of one volt.
Threshold Frequency
The minimum frequency of electromagnetic radiation required to eject an electron from a metal surface during the photoelectric effect.
Work Function
The minimum energy of electromagnetic radiation required to eject an electron from a metal surface during the photoelectric effect.
De Broglie Wavelength
The wavelength associated with a particle with mass. It depends on the particle’s momentum.
