Cambridge IGCSE Physics4.2 Electrical quantities Checklist
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What's on this checklist
Core
- I can state that there are positive charges and negative charges.
- I can state that positive charges repel other positive charges and negative charges repel other negative charges, but positive charges attract negative charges.
- I can describe simple experiments that show electrostatic charges being produced by friction, and that show how electrostatic charges are detected.
- I can explain that charging solids by friction involves the transfer of negative charge (electrons) only.
- I can describe an experiment to tell electrical conductors from insulators.
- I can recall and use a simple electron model to explain the difference between electrical conductors and insulators, and give typical examples of each.
- I know that electric current is related to the flow of charge.
- I can describe how ammeters (analogue and digital) with different ranges are used.
- I can describe electrical conduction in metals in terms of the movement of free electrons.
- I know the difference between direct current (d.c.) and alternating current (a.c.).
- I can define electromotive force (e.m.f.) as the electrical work done by a source in moving a unit charge around a complete circuit.
- I know that e.m.f. is measured in volts (V).
- I can define potential difference (p.d.) as the work done by a unit charge passing through a component.
- I know that the p.d. between two points is measured in volts (V).
- I can describe how voltmeters (analogue and digital) with different ranges are used.
- I can recall and use the equation for resistance, R = V/I.
- I can describe an experiment to find resistance using a voltmeter and an ammeter, and do the calculations needed.
- I can state, qualitatively, how the resistance of a metallic wire is related to its length and to its cross-sectional area.
- I understand that electric circuits transfer energy from a source of electrical energy, such as an electrical cell or the mains supply, to the circuit components and then into the surroundings.
- I can recall and use the equation for electrical power, P = IV.
- I can recall and use the equation for electrical energy, E = IVt.
- I can define the kilowatt-hour (kW h), and calculate the cost of using electrical appliances when the energy unit is the kW h.
Extended
- I can state that charge is measured in coulombs.
- I can describe an electric field as a region in which an electric charge experiences a force.
- I can state that the direction of an electric field at a point is the direction of the force on a positive charge placed at that point.
- I can describe simple electric field patterns, including the direction of the field:a)around a point chargeb)around a charged conducting spherec)between two oppositely charged parallel conducting plates (end effects are not examined)
- I can define electric current as the charge passing a point per unit time, and I can recall and use the equation I = Q/t.
- I can state that conventional current goes from positive to negative, and that free electrons flow from negative to positive.
- I can recall and use the equation for e.m.f., E = W/Q.
- I can recall and use the equation for p.d., V = W/Q.
- I can sketch and explain the current–voltage graphs for a resistor of constant resistance, a filament lamp and a diode.
- I can recall and use these relationships for a metallic electrical conductor:a)resistance is directly proportional to lengthb)resistance is inversely proportional to cross-sectional area