- Need help?
CAIE
9. Electricity
9.1 Electric current
- understand that an electric current is a flow of charge carriers
- understand that the charge on charge carriers is quantised
- recall and use Q = It
- use, for a current-carrying conductor, the expression I = Anvq, where n is the number density of charge carriers
9.2 Potential difference and power
- define the potential difference across a component as the energy transferred per unit charge
- recall and use V = W/Q
- recall and use P = VI, P = I 2 R and P = V2 /R
9.3 Resistance and resistivity
- define resistance
- recall and use V = IR
- sketch the I–V characteristics of a metallic conductor at constant temperature, a semiconductor diode and a filament lamp
- explain that the resistance of a filament lamp increases as current increases because its temperature increases
- state Ohm’s law
- recall and use R = ρL /A
- understand that the resistance of a light-dependent resistor (LDR) decreases as the light intensity increases
- understand that thunderstand that the resistance of a thermistor decreases as the temperature increases (it will be assumed that thermistors have a negative temperature coefficient)e resistance of a light-dependent resistor (LDR) decreases as the light intensity increases