DC Circuits JPJC Notes

1 JURONG PIONEER JUNIOR COLLEGE 9749 H2 PHYSICS D.C. 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.

2 Introduction • In the previous topic on Current of Electricity, physical quantities such as electromotive force (e.m.f.), potential difference (p.d), current (I), resistance (R) and internal resistance (r) in electric circuits were discussed. • This topic on Direct Current (D.C.) Circuits involves electric circuits with current that flows in one direction. 1 Circuit symbols and diagrams (a) Candidates should be able to 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) Candidates should be able to draw and interpret circuit diagrams containing sources, switches, resistors, ammeters, voltmeters, and/or any other type of component referred to in the syllabus. 1.1 Circuit symbols wires crossed, wires joined, not joined junction of conductors signal lamp filament lamp fuse heater fixed resistor variable resistor light-sensitive light-emitting potential divider resistor (LDR) thermistor diode (LED) switch voltmeter ammeter galvanometer (open) Fig. 1 Circuit Symbols A V

3 2 Series and parallel arrangements (c) Candidates should be able to s olve problems using the formula for the combined resistance of two or more resistors in series. When two or more resistors are connected using connecting wires, the combined effect of these resistors can be represented by drawing a single resistor