Un 2 capacitors

Question 1

Variation of current in a capacitor

Answer 1

Decreases from a supply current value to 0 as it charges
Increases exponentially from negative of supply current to zero as it discharges

Question 2

Variation of voltage in a capacitor

Answer 2

Increases exponentially from 0 to supply voltage as it charges.
Decreases exponentially from supply voltage to zero as it discharges

Question 3

Variation of charge in a capacitor

Answer 3

Increases exponentially over time from 0 to a max value as it charges
Decreases exponentially from a max value to zero over time as it discharges

Question 4

Variation of current in a circuit with a capacitor (no answer)

Question 5

Variation of voltage in a circuit with a capacitor (no answer)

Question 6

Variation of charge in a circuit with a capacitor (no answer)

Question 7

Factors affecting time taken for a capacitor to charge

Answer 7

Resistance of the resistor R (as it controls size of the current)
Capacitance of the capacitor (a larger capacitor will take longer to “fill” and “empty”)

Question 8

Relationship between resistance in a resistor R and time taken for a capacitor to charge or discharge

Answer 8

As the resistance increases the time taken for the capacitor to charge or discharge also increases

Question 9

Relationship between the capacitance in a capacitor and the time taken for a capacitor to charge or discharge

Answer 9

As the capacitance in a capacitor increases the time taken for the capacitor to charge or discharge also increases.

Question 10

Area under the current-time graph of a capacitor equals:

Answer 10

Charge

Question 11

Definition of time constant for an RC circuit

Answer 11

The time to increase the charge stored by 63% of the difference between initial charge and full charge / for the charge to increase to 63% of its final value
OR
the time taken to discharge the capacitor to 37% of initial charge

Question 12

State the use of and define the symbols in
t = RC

Answer 12

Used to calculate the time constant in an RC circuit
t - time constant (s)
R - Resistance of resistor R (Ohms)
C - Capacitance of capacitor (F)

Question 13

In an RC circuit, an uncharged capacitor can be considered to be fully
CHARGED after a time approximately equal to what?

Answer 13

5t

Question 14

In an RC circuit, a fully charged capacitor can be considered to be fully
DISCHARGED after a time approximately equal to what?

Answer 14

5t

Question 15

Definition of capacitive Reactance (X(c))

Answer 15

The opposition of a capacitor to changing current.

Question 16

State the use of and define the symbols in
X(c) = V/I

Answer 16

Used to calculate the capacitive reactance in a capacitive circuit
X(c) - Capacitive reactance (Ohms)
V - Potential difference (V)
I - Current (A)

Question 17

Relationship between current in a resistive circuit and frequency

Answer 17

The current in a resistive circuit remains constant with frequency. ( I = V/R)
Resistors are unaffected by the frequency of the supply and behave in the same way in both D.C and A.C circuits