ASRJC D.C. Circuits Notes

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 15-1 Additional Notes Topic 15: D.C. Circuits Content A Circuit symbols and diagrams B Series and parallel arrangements C Potential divider D 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

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 15-2 Additional Notes A Circuit symbols and diagrams A.1 Introduction Direct circuit • Direct current (in short d.c.) refers to current which flows in one direction only . In contrast, alternating current (in short a.c.) refers to current which changes direction periodically. • Direct current must be one-directional, not necessarily constant magnitude, i.e. it need not be a steady current In Fig. 15.1, Graph ( a), Graph ( b) and Graph ( c) show examples of direct current whereas Graph (d) and Graph (e) show examples of alternating current Fig. 15.1 time current time current time current time current time current Graph (a) Graph (b) Graph (c) Graph (d) Graph (e)

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 15-3 Additional Notes Circuit symbols Symbol Description Symbol Description Switch Electric bell Fixed resistor Heater Variable resistor Thermistor Voltmeter Potential divider Ammeter Loudspeaker Galvanometer Lamp Cell Capacitor * Battery of cells Inductor * D.C. power supply Transformer with core Aerial * Microphone * Fuse Motor * Diode Light emitting diode (LED) Light Dependent Resistor (LDR) Earth Cross (no connection between wires) Junction connection (wires physically connected) Double junction connection Frame or chassis connection * *Less common in the H2 A-Level syllabus Fig. 15.2

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 15-4 Additional Notes Ammeter • An ammeter measures th