Transients

Select the corrent sentence regarding a resistor and uncharged capacitor suddenly connected to a DC supply:

• Kirchhoff’s Voltage Law shows that v_R and v_C are complementary.

• The resistor voltage rises as time goes by whilst the capacitor voltage falls.

• The current in the circuit is zero initially.

• In a time equal to one time constant the current falls to 63% approximately of its starting value.

A 100 nF capacitor and 10 kΩ resistor are connected in series. Select the correct value of the time constant:

• 1 s

• 1000 s

• 1 μs

• 1 ms

Select the correct statement regarding a series resistor-inductor circuit suddenly connected to a DC supply:

• If the initial rate of growth of current in an inductor were to continue, it would reach its final value in five time constants.

• The voltage across the DC source and the resistor are complementary.

• The voltage across the inductor falls to 37% of its starting value

  after 1 time constant.

• The voltage across the inductor rises as the current in it rises.

Select the correct value of time constant for a circuit containing a 1 mH inductor with a resistance of 50 Ω:

• 0.05 s

• 50 μs

• 20 μs

• 20 ns

A 1000 μF capacitor is being charged from a 12 V DC supply through a 1000 Ω resistor. Select how long it takes to reach 7.56 V:

• 1 ms

• 1 s

• 5 ms

• 5 s

A 10 mH inductor with a resistance of 25Ω is suddenly connected to a 50 V DC supply. Approximately how long will it take the current to reach 2 A?

• 0.4 ms

• 2 ms

• 250 ms

• 400 ms