19. Capacitance
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19.1 Capacitors and capacitance
19.1.1Capacitance, as applied to both isolated spherical conductors and to
• define capacitance, as applied to both isolated spherical conductors and to parallel plate capacitors
19.1.2C = Q / V
• recall and use C = Q / V
19.1.3C = Q / V, formulas for the combined capacitance of capacitors in series and
• derive, using C = Q / V, formulas for the combined capacitance of capacitors in series and in parallel
19.1.4The capacitance formulas for capacitors in series and in parallel
• use the capacitance formulas for capacitors in series and in parallel
19.2 Energy stored in a capacitor
• determine the electric potential energy stored in a capacitor from the area under the potential–charge graph
• recall and use W = 1/2 QV = 1/2 CV 2
19.3 Discharging a capacitor
• analyse graphs of the variation with time of potential difference, charge and current for a capacitor discharging through a resistor
• recall and use τ = RC for the time constant for a capacitor discharging through a resistor
• use equations of the form x = x0 e–(t / RC) where x could represent current, charge or potential difference for a capacitor discharging through a resistor