Electricity and Magnetism - SS2 Physics Past Questions and Answers - page 3
In an RC circuit, the time constant is defined as the time it takes for the voltage across the capacitor to reach what percentage of its maximum value?
25%
50%
63%
75%
In an RC circuit, the time constant is determined by which of the following quantities?
Resistance (R) only
Capacitance (C) only
Both Resistance (R) and Capacitance (C)
Voltage (V) across the capacitor
A capacitor in an RC circuit is initially fully charged. How many time constants does it take for the voltage across the capacitor to decrease to approximately 5% of its initial value?
1 time constant
2 time constants
3 time constants
4 time constants
If the capacitance in an RC circuit is doubled while keeping the resistance constant, how does the time constant change?
It remains the same
It is halved
It is doubled
It is quadrupled
In an RC circuit, the charging time constant is given by the product of the resistance and capacitance. If the resistance is increased while the capacitance is kept constant, what happens to the charging time constant?
It decreases
It increases
It remains the same
It cannot be determined without more information
In an RC circuit, the resistance is 100 ohms and the capacitance is 10 microfarads. Calculate the time constant of the circuit.
Time constant (τ) = RC
= (100 ohms) x (10 microfarads) = 1 millisecond
In an RC circuit, the time constant is 5 seconds. If the capacitance is 20 microfarads, what is the value of the resistance?
Resistance (R) = τ / C
= (5 seconds) / (20 microfarads)
= 250,000 ohms = 250 kilohms
In an RC circuit, the initial voltage across the capacitor is 12 volts. After one time constant, the voltage decreases to 3 volts. What is the percentage of voltage remaining after one time constant?
Percentage of voltage remaining = (Voltage after one time constant / Initial voltage) x 100% = (3 volts / 12 volts) x 100% = 25%
In an RC circuit, the time constant is 2 milliseconds. If the capacitance is 4 microfarads, what is the value of the resistance?
Resistance (R) = τ / C
= (2 milliseconds) / (4 microfarads) = 500 ohms
In an RC circuit, the resistance is 1 kilohm and the time constant is 10 microseconds. What is the capacitance of the circuit?
Capacitance (C) = τ / R
= (10 microseconds) / (1 kilohm) = 10 nanofarads