4.3-Electric circuits

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Syllabus Objectives

4.3.1 Circuit diagrams and circuit components

CORE OBJECTIVES:

  • Draw and interpret circuit diagrams containing cells, batteries, power supplies, generators, potential dividers, switches, resistors (fixed and variable), heaters, thermistors (NTC only), light-dependent resistors (LDRs), lamps, motors, ammeters, voltmeters, magnetising coils, transformers, fuses and relays, and know how these components behave in the circuit

EXTENDED/SUPPLEMENT OBJECTIVES:

  • Draw and interpret circuit diagrams containing diodes and light-emitting diodes (LEDs), and know how these components behave in the circuit

4.3.2 Series and parallel circuits

CORE OBJECTIVES:

  • Know that the current at every point in a series circuit is the same
  • Know how to construct and use series and parallel circuits
  • Calculate the combined e.m.f. of several sources in series
  • Calculate the combined resistance of two or more resistors in series
  • State that, for a parallel circuit, the current from the source is larger than the current in each branch
  • State that the combined resistance of two resistors in parallel is less than that of either resistor by itself
  • State the advantages of connecting lamps in parallel in a lighting circuit

EXTENDED/SUPPLEMENT OBJECTIVES:

  • Recall and use in calculations, the fact that:
  • (a) the sum of the currents entering a junction in a parallel circuit is equal to the sum of the currents that leave the junction
  • (b) the total p.d. across the components in a series circuit is equal to the sum of the individual p.d.s across each component
  • (c) the p.d. across an arrangement of parallel resistances is the same as the p.d. across one branch in the arrangement of the parallel resistances
  •  Explain that the sum of the currents into a junction is the same as the sum of the currents out of the junction
  • Calculate the combined resistance of two resistors in parallel

4.3.3 Action and use of circuit components

CORE OBJECTIVES:

  • Know that the p.d. across an electrical conductor increases as its resistance increases for a constant current

Revision Notes

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