Electrical Transients

A series RL circuit is connected across a dc source through a switch. Three milliseconds after the switch is closed, the voltage across the inductance is 20 V, and it drops to 5 V after 25 ms. If R = 100 ohms, find L. Assume at t = 0, i = 0.

A 2 μF capacitor with an initial charge of 100 μC is connected across a 100 Ω resistor at t = 0. Calculate the time in which the transient voltage across the resistor drops from 40 to 10 volts.

A 1.5 MΩ resistor is connected in series with a 20 μF capacitor. The voltage source is 120 volts dc. Determine the current at t = 10 seconds after the switch is closed.

A capacitor of 40 μF capacitance in series with 2,000 ohms is suddenly connected across a 200-volt source. What is the energy stored in the capacitor after 0.04 sec?

The current in a coil decays as follows: when t = 0.002 s the current is 10 mA; when t = 0.006 s the current drops to 4 mA. The time constant of the coil is _______.

A 1.5 MΩ resistor is connected in series with a 20 μF capacitor. The voltage source is 120 volts dc. Determine the time at which the voltage across the capacitor is 75% of the source voltage.

The field circuit of a 4-pole dc generator has a resistance of 200 Ω and an inductance of 100 H. If it is connected to a 400 V supply, find the time taken for the current to reach 1.5 A.

A 60 μF capacitor is connected in series with a 40,000 Ω resistor. If the capacitor is initially uncharged, determine the resistor voltage when t = 1.5 time constants for a suddenly applied source emf of 120 volts.

A coil having a resistance of 10 Ω and an inductance of 4 H is switched across a 20 V dc source. Calculate the rate of current change when the current reaches 50% of its final steady value.