A parallel plate capacitor is made up of two conductive plates with opposite charges building up on each plate
Graphs of variation of current, p.d and charge with time for a capacitor charging through a battery
The capacitor charges when connected to terminal P and discharges when connected to terminal Q
Graphs of variation of current, p.d and charge with time for a capacitor discharging through a resistor
ΔQ = IΔt
The area under the I-t graph is the total charge stored in the capacitor in the time interval Δt
The gradient of a discharging and charging Q-t graph is the current
The graph below shows how the charge stored on a capacitor with capacitance C varies with time as it discharges through a resistor.
Calculate the current through the circuit after 4 s.
Step 1: Draw a tangent at t = 4
Step 2: Calculate the gradient of the tangent to find the current I
Make sure you're comfortable with sketching and interpreting charging and discharging graphs, as these are common exam questions.
Remember that conventional current flow is in the opposite direction to the electron flow