DHS 10 D.C. Circuits (Lecture Notes & Tutorial)

1 9749 Physics (2024) Topic 15: D.C. Circuits Guiding Questions • How are symbols and diagrams used to represent real circuits? • How are the principles of charge and energy conservation applied to analyse circuits? Content • Circuit symbols and diagrams • Series and parallel arrangements • Potential divider • Balanced potentials Learning Outcomes Candidates should be able to: (a) recall and use appropriate circuit symbols as set out in the ASE publication Signs, symbols and systematics: the ASE companion to 16-19 science (2000) (b) draw and interpret circuit diagrams containing sources, switches, resistors, ammeters, voltmeters, and/or any other type of component referred to in the syllabus (c) solve problems using the formula for the combined resistance of two or more resistors in series (d) solve problems using the formula for the combined resistance of two or more resistors in parallel (e) solve problems involving series and parallel circuits for one source of e.m.f. (f) show an understanding of the use of a potential divider circuit as a source of variable p.d. (g) explain the use of thermistors and light -dependent resistors in potential divider circuits to provide a potential difference which is dependent on temperature and illumination respectively (h) recall and solve problems by using the principle of the potentiometer as a means of comparing potential differences. 9749 H2 Physics Topic 15 D.C. Circuits Year 5 (2024) DUNMAN HIGH SCHOOL

2 9749 Physics (2024) Topic 15: D.C. Circuits Introduction D.C. stands for direct current. It means current flowing only in one direction in a closed circuit. The magnitude of the current, however, may vary from time to time. The following are some examples of graphs representing the variation of direct current with time. In (a) and (b), the magnitudes of the current change with time. The currents in (a) and (b) flow in the opposite direction. In (c), the current flows with constant magnitude. We say, the current is a steady D.C. This chapter focuses mainly on the type of current shown in (c) – steady D.C. A simple D.C. circuit will usually comprise: a) source (s), e.g. batteries, cells b) switches c) resistors (or other components such as capacitors) d) measuring instruments such as voltmeter, ammeter, etc. time current time current time current (a) (b) (c)

3 9749 Physics (2024) Topic 15: D.C. Circuits (a) recall and use appropriate circuit symbols as set out in the ASE publication Signs, symbols and systematics: the ASE companion to 16-19 science (2000) (b) draw and interpret circuit diagrams containing sources, switches, resistors, ammeters, voltmeters, and/or any other type of component referred to in the syllabus Standard circuit symbols are used to simplify circuit diagrams. Each circu