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 travels from positive terminal to the negative terminal
Conversation of charge
Charge is conserved in all interactions; it cannot be created or destroyed
Coulomb
1 Coulomb of electric charge passes a point in 1 second when there is an electric current of 1 ampere flowing
Ampere
The current flowing in two parallel wires in a vacuum 1 metre apart such that there is an attractive force of 2 x 10^-7N per metre length of wire between them.
Electrolyte
A fluid that contains ions that are free to move and hence conduct electricity
Number Density
The number of delocalised electrons per metre cubed of the material
Conductor
A material with a high number density of conduction electrons and therefore a low resistance
Insulator
A material with a small number density of conduction electrons and therefore a very high resistance
Mean Drift Velocity
The average velocity of electrons as they move through a wire
Electromotive force (EMF)
EMF is the energy transferred per unit charge when one type of 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
2 points in a circuit are at a potential difference of 1V if 1J of energy is transferred when 1C of charge passes from 1 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
A conductor has a resistance of one ohm if there a pd of one volt across it when a current of one ampere flows through it
Ohm’s law
For a metallic conductor at constant temperature, the current in the conductor is directly proportional to the potential difference across its ends.
Resistivity
The resistivity of a material is the product of its resistance and its cross-sectional area per unit length
Kilowatt-Hour
Energy dissipated by a 1kW electrical device in a time of one hour which is equivalent to 3.6MJ
Kirchhoff’s First Law
The sum of the currents entering any point in an electrical circuit is always equal to the sum of the currents leaving that point, as charge is conserved
Kirchhoff’s Second Law
The sum of the EMF’s around any closed loop in a circuit is equal to the sum of the PD’s around the same closed loop.
Internal Resistance
Some energy is transformed into thermal energy within the cell; the cell behaves as if it had a resistance.
Progressive wave
A transfer of energy as a result of the oscillations of the medium or particles through which the energy is travelling.
Longitudinal wave
A wave whereby the oscillations of the particles of the medium are parallel to the direction of travel
Displacement
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 transmitted by the wave
Frequency
The number of oscillations at a point per unit time
Period
The time taken for 1 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 oscillate in 1 plane only
Intensity
The rate of energy incident per unit area at right angles to the direction of propagation
Interference
When 2 or more 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 another wave
Coherent Sources
Sources of waves which have a constant phase difference
Node
A point where the amplitude of vibrations is always zero
Antinode
A point where the amplitude of vibrations takes the maximum possible value.
