BRAINCAKEElectric Current
Revision notes for Electric Current in AQA Physics (7407). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Electrical ConductionElectrons are the charge carriers in metals.
- Electric Current and Electric ChargeCurrent is the flow of charge.
- Charge CarriersInsulators No electrons move through insulators because there are no free electrons that can move through the solid lattice.
- The Emf of a SourceThe e.m.f. is the work done per unit charge i.e. the electrical energy produced by the source.
- Potential DifferenceThe potential difference is the energy transferred per unit charge by the charge carriers to the component.
- Energy TransferThe electrical power is the energy transferred per unit time by the charge carriers to the component.
- Electric PowerThe electrical power is the energy transferred per unit time by the charge carriers to the component.
- ResistanceThe electrical resistance of a component is a measure of its opposition to the flow of electric current through it.
- Measuring Resistanceresistance = p.d. across component current through component R = V I ohms = volts amps The current is varied using a variable resistor and measured…
- Ohm's LawThe p.d. across a metallic conductor is directly proportional to the current through it provided the physical conditions are the same.
- ResistivityR = ρ L A resistance = resistivity × ;length(m) cross-section area(m2). ρ is resistivity, L is the length ot the wire and A is the cross-sectional…
- SuperconductivitySuperconductor materials have zero resistivity below a critical temperature e.g. -123°C for compounds containing mercury, barium, calcium, copper…
- Electronic ComponentsVariable Resistor Varies current.
- Investigating the Characteristics of ComponentsTo measure the variation of current with potential difference for a component, either a potential divider circuit or a variable resistor can be used…
- IV GraphsOhmic resistor, non-ohmic resistor such as a filament lamp, semiconductor diode with threshold voltage of 0.6V and LDR/thermistor.
- Fixed ResistorsWhen an IV graph is plotted, a wire gives a straight line through the origin.
- Filament LampThe I-V graph for a filament lamp is a non-linear, s-shaped curve passing through the origin, because the current is not directly proportional to…
- Thermistors and Light Dependent ResistorsA thermistor is made from an intrinsic semi-conducting material such as silicon.
- DiodesThe current through a diode is measured for a range of potential differences in both the forward and reverse bias.
- Resistance and TemperatureThe resistance of a metal increases with temperature.