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9. Electricity

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  1. 9.1 Electric current

    1. • understand that an electric current is a flow of charge carriers

    2. • understand that the charge on charge carriers is quantised

    3. • recall and use Q = It

    4. • use, for a current-carrying conductor, the expression I = Anvq, where n is the number density of charge carriers

  2. 9.2 Potential difference and power

    1. • define the potential difference across a component as the energy transferred per unit charge

    2. • recall and use V = W / Q

    3. • recall and use P = VI, P = I 2R and P = V 2 / R

  3. 9.3 Resistance and resistivity

    1. 9.3.1Resistance

      • define resistance

    2. 9.3.2V = IR

      • recall and use V = IR

    3. 9.3.3The I–V characteristics of a metallic conductor at constant temperature, a

      • sketch the I–V characteristics of a metallic conductor at constant temperature, a semiconductor diode and a filament lamp

    4. 9.3.4That the resistance of a filament lamp increases

      • explain that the resistance of a filament lamp increases as current increases because its temperature increases

    5. 9.3.5Ohm’s law

      • state Ohm’s law

    6. 9.3.6R = ρL / A

      • recall and use R = ρL / A

    7. 9.3.7The resistance of a light-dependent resistor (LDR) decreases

      • understand that the resistance of a light-dependent resistor (LDR) decreases as the light intensity increases

    8. 9.3.8The resistance of a thermistor decreases as the temperature increases (it

      • understand that the resistance of a thermistor decreases as the temperature increases (it will be assumed that thermistors have a negative temperature coefficient)