Learning objectives
Describe current as the rate of flow of charge carriers such as electrons or ions, explain that charge comes in whole multiples of e, and use Q = It.
Use I = Anvq to relate current to the number density and drift velocity of charge carriers in metals and semiconductors.
Define the potential difference across a component in terms of energy transferred per unit charge, and calculate electrical energy and power with V = W/Q, P = VI, P = I²R and P = V²/R.
Define resistance, state Ohm's law, and use V = IR and R = ρL/A to relate resistance to the resistivity and dimensions of a conductor.
Sketch I–V graphs for a metal wire at constant temperature, a filament lamp and a semiconductor diode, and explain the lamp's curve by the rise in filament temperature and resistance.
Describe how the resistance of a light-dependent resistor falls as light intensity rises and that of an NTC thermistor falls as temperature rises.
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