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1. The graph shows how the potential difference across a capacitor varies with time as it discharges through a resistor.
(i) What is the time constant for the circuit?
(ii) Calculate the capacitance of the capacitor if the resistor were 100 kΩ
(iii) What is the half-life of the circuit.
2. The graph shows how the potential difference across a capacitor varies with time as it discharges through a resistor.
(i) What is the time constant for the circuit?
(ii) Calculate the resistance of the circuit if the capacitance of the capacitor were 100 μF.
3.
The time constant for a capacitor-resistor circuit is 0.5 s.
The electrical capacitance of the capacitor is 500 pF and the potential
difference across the capacitor before it started discharging was 10.0 V.
Calculate:
(a) The electrical resistance of
the circuit
(b) the initial charge on the
capacitor
(c) the potential difference across
the capacitor after 1.0 s
(d) the charge on the capacitor’s
plates after 1.0 s
(e) the charge that leaves the positive plate in 1.0 s
(f) the electric current in the
circuit after 1.0 s.
4.
The time constant for a capacitor-resistor circuit is 400 ms.
The electrical capacitance of the capacitor is 47 pF and the potential
difference across the capacitor before it started discharging was 3.0 V.
Calculate:
(a) The electrical resistance of
the circuit
(b) the initial charge on the
capacitor
(c) the potential difference across
the capacitor after 700 ms
(d) the charge on the capacitor’s
plates after 700 ms
(e) the charge that leaves the positive plate in 700 ms
(f) the electric current in the
circuit after 700 ms.
5.
The time constant of a capacitor-resistor circuit is 25 s, the
electrical resistance of the circuit is 50 kΩ. The initial current that
flows when the capacitor begins to discharge is 50 mA, calculate:
(a) the current flowing after 12.5
s
(b) the charge on the plates after
50 s
(c) the charge that leaves the
plates in the first 25 s
(d) the potential difference across
the capacitor after 25 s.
6. Calculate the charge that leaves the plates during the period marked on the graph below. The capacitance of the discharging capacitor is 100 nF.
7.
The graph below illustrates how the potential difference
across a capacitor varies as it is charged with a resistor in series with it
and a 12 V battery.
(a) Estimate the time constant for the circuit.
(b) The charge that moves onto the
plates between 6 and 17 seconds
8.
The same circuit used in question seven has a graph of I (in
A) vs t for the same charging period shown here:
Calculate:
(a) The electrical resistance of the
circuit
(b) The capacitance of the capacitor