Electric Circuits

Current, Voltage and ResistanceSign up

understand that electric current is the rate of flow of charged particles and be able to use the equation I = Q/t · understand how to use the equation V = W/Q · understand that resistance is defined by R = V/I and that Ohm's law is a special case when I is proportional to V for constant temperature

Circuit Laws and PowerSign up

(a) understand how the distribution of current in a circuit is a consequence of charge conservation. (b) understand how the distribution of potential differences in a circuit is a consequence of energy conservation · be able to derive the equations for combining resistances in series and parallel using the principles of charge and energy conservation, and be able to use these equations · be able to use the equations P = VI, W = VIt and be able to derive and use related equations, e.g. P = I^2 R and P = V^2/R · understand how to sketch, recognise and interpret current-potential difference graphs for components, including ohmic conductors, filament bulbs, thermistors and diodes

Resistivity and ConductionSign up

be able to use the equation R = rho l / A · CORE PRACTICAL 7: Determine the electrical resistivity of a material · be able to use I = nqvA to explain the large range of resistivities of different materials · understand how changes of resistance with temperature may be modelled in terms of lattice vibrations and number of conduction electrons and understand how to apply this model to metallic conductors and negative temperature coefficient thermistors · understand how changes of resistance with illumination may be modelled in terms of the number of conduction electrons and understand how to apply this model to LDRs.

Potential Dividers and Internal ResistanceSign up

understand how the potential along a uniform current-carrying wire varies with the distance along it · understand the principles of a potential divider circuit and understand how to calculate potential differences and resistances in such a circuit · be able to analyse potential divider circuits where one resistance is variable including thermistors and light dependent resistors (LDRs) · know the definition of electromotive force (e.m.f.) and understand what is meant by internal resistance and know how to distinguish between e.m.f. and terminal potential difference · CORE PRACTICAL 8: Determine the e.m.f. and internal resistance of an electrical cell