Physics Topic: Circuits

  1. Recall and use appropriate circuit symbols as set out in the current ASE Report — SI Units, Signs, Symbols and Abbreviations.

  2. Draw and interpret circuit diagrams containing sources, switches, resistors, ammeters, voltmeters, and/or any other types of component referred to in the syllabus.

  3. define the resistance of a circuit component as the ratio of the potential difference across the component to the current in it, and solve problems using the equation V = IR

  4. recall and solve problems using the equation relating resistance to resistivity, length and cross-sectional area, R = ρ l / A

  5. sketch and interpret the I–V characteristics of various electrical components in a d.c. circuit, such as an ohmic resistor, a semiconductor diode, a filament lamp and a negative temperature coefficient (NTC) thermistor

  6. explain the temperature dependence of the resistivity of typical metals (e.g. in a filament lamp) and semiconductors (e.g. in an NTC thermistor) in terms of the drift velocity and number density of charge carriers respectively

  7. show an understanding of the effects of the internal resistance of a source of e.m.f. on the terminal potential difference and output power

  8. Recall and solve problems by using the principle of the potentiometer as a means of comparing potential differences.

  9. solve problems using the formula for the combined resistance of two or more resistors in series

  10. solve problems using the formula for the combined resistance of two or more resistors in parallel

  11. solve problems involving series and parallel arrangements of resistors for one source of e.m.f., including potential divider circuits which may involve NTC thermistors and light-dependent resistors

  12. solve problems using the formulae for the combined capacitance of two or more capacitors in series and in parallel

  13. describe and represent the variation with time, of quantities like current, charge and potential difference, for a capacitor that is charging or discharging through a resistor, using equations of the form x = x0 e(-t/τ) or x = x0 [1 – e(-t/τ)] where τ = RC is the time constant.