Episode 113: Preparation for series and parallel circuits topic

Advance warning

Potential divider - potentiometer

A joulemeter will be useful when discussing energy and power in electric circuits. It is worth practising with it before using it in any demonstration.

Find a selection of ready-made potential dividers (also known as potentiometers). Look for the three connections, characteristic of a potential divider. Take the back off a rotary potentiometer to see the resistive material, and the wiper.

Main aims
Students will:

  • calculate resistances of series and parallel combinations of resistors
  • investigate the power of a filament lamp
  • use energy and power equations, including calculations of cost
  • test and use Kirchhoff's laws
  • use potential dividers to control potential difference and to build a sensor

Prior knowledge
By this stage, students should be able to distinguish between charge, current and voltage; they should understand the definition of resistance, and be competent in handling equations involving these four quantities. However some pupils will probably still be unwittingly harbouring some misconceptions, for example in the area of potential differences in parallel circuits, so be prepared to test, rather than to assume knowledge. These misconceptions may well become apparent in the Episodes 117 and 118.

This topic also revisits ideas about energy transfers in electric circuits.

Where this leads
Topics remaining in basic electricity include EMF and internal resistance. Then students will be equipped to understand many different circuits, alternating current, etc.

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