Electrical Quantities

State that there are positive and negative charges

State that positive charges repel other positive charges, negative charges repel other negative charges, but positive charges attract negative charges

Describe simple experiments to show the production of electrostatic charges by friction and to show the detection of electrostatic charges

Explain that charging of solids by friction involves only a transfer of negative charge (electrons)

Describe an experiment to distinguish between electrical conductors and insulators

Recall and use a simple electron model to explain the difference between electrical conductors and insulators and give typical examples

State that charge is measured in coulombs

Describe an electric field as a region in which an electric charge experiences a force

State that the direction of an electric field at a point is the direction of the force on a positive charge at that point

Describe simple electric field patterns, including the direction of the field: (a) around a point charge (b) around a charged conducting sphere (c) between two oppositely charged parallel conducting plates (end effects will not be examined)

Know that electric current is related to the flow of charge

Describe the use of ammeters (analogue and digital) with different ranges

Describe electrical conduction in metals in terms of the movement of free electrons

Know the difference between direct current (d.c.) and alternating current (a.c.)

Define electric current as the charge passing a point per unit time; recall and use the equation Q I = t

State that conventional current is from positive to negative and that the flow of free electrons is from negative to positive

Define electromotive force (e.m.f.) as the electrical work done by a source in moving a unit charge around a complete circuit

Know that e.m.f. is measured in volts (V)

Define potential difference (p.d.) as the work done by a unit charge passing through a component

Know that the p.d. between two points is measured in volts (V)

Describe the use of voltmeters (analogue and digital) with different ranges

Recall and use the equation for e.m.f. W E = Q

Recall and use the equation for p.d. W V = Q

Recall and use the equation for resistance V R = I

Describe an experiment to determine resistance using a voltmeter and an ammeter and do the appropriate calculations

State, qualitatively, the relationship of the resistance of a metallic wire to its length and to its cross-sectional area

Recall and use the following relationship for a metallic electrical conductor: (a) resistance is directly proportional to length (b) resistance is inversely proportional to cross-sectional area

Understand that electric circuits transfer energy from a source of electrical energy, such as an electrical cell or mains supply, to the circuit components and then into the surroundings

Recall and use the equation for electrical power P = IV

Recall and use the equation for electrical energy E = IVt

Define the kilowatt-hour (kW h) and calculate the cost of using electrical appliances where the energy unit is the kW h

Draw and interpret circuit diagrams containing cells, batteries, power supplies, generators, potential dividers, switches, resistors (fixed and variable), heaters, thermistors (NTC only), light- dependent resistors (LDRs), lamps, motors, bells, ammeters, voltmeters, magnetising coils, transformers, fuses and relays and know how these components behave in the circuit

Draw and interpret circuit diagrams containing diodes and light-emitting diodes (LEDs) and know how these components behave in the circuit

Know that the current at every point in a series circuit is the same

Know how to construct and use series and parallel circuits

Calculate the combined e.m.f. of several sources in series

Calculate the combined resistance of two or more resistors in series

State that, for a parallel circuit, the current from the source is larger than the current in each branch

State that the combined resistance of two resistors in parallel is less than that of either resistor by itself

State the advantages of connecting lamps in parallel in a lighting circuit

Recall and use in calculations, the fact that: (a) the sum of the currents entering a junction in a parallel circuit is equal to the sum of the currents that leave the junction (b) the total p.d. across the components in a series circuit is equal to the sum of the individual p.d.s across each component (c) the p.d. across an arrangement of parallel resistances is the same as the p.d. across one branch in the arrangement of the parallel resistances

Explain that the sum of the currents into a junction is the same as the sum of the currents out of the junction

Calculate the combined resistance of two resistors in parallel