The heating effects of electric current

Understandings:

• Electric current
• Direct current (dc)
• Circuit diagrams
• Kirchhoff’s circuit laws
• Heating effect of current and its consequences
• Resistance expressed as R=VI
• Ohm’s law
• Resistivity
• Power dissipation

Applications and skills:

• Drawing and interpreting circuit diagrams
• Identifying sign and nature of charge carriers in a metal
• Identifying drift speed of charge carriers
• Solving problems using the drift speed equation
• Solving problems involving current, potential difference and charge
• Identifying ohmic and non-ohmic conductors through a consideration of the V/I characteristic graph
• Solving problems involving potential difference, current, charge, Kirchhoff’s circuit laws, power, resistance and resistivity
• Investigating combinations of resistors in parallel and series circuits
• Describing ideal and non-ideal ammeters and voltmeters
• Describing practical uses of potential divider circuits, including the advantages of a potential divider over a series resistor in controlling a simple circuit
• Investigating one or more of the factors that affect resistance experimentally

Guidance:

• The filament lamp should be described as a non-ohmic device; a metal wire at a constant temperature is an ohmic device
• The use of non-ideal voltmeters is confined to voltmeters with a constant but finite resistance
• The use of non-ideal ammeters is confined to ammeters with a constant but non-zero resistance
• Application of Kirchhoff’s circuit laws will be limited to circuits with a maximum number of two source-carrying loops