IEE1 (10)

The field circuit of a 4-pole dc motor has a resistance of 2000 and an inductance of 100 H. If it is connected to a 400-volt supply, find the time taken for the current to reach 1.5 A

• 0.125 sec

• 1.5 sec

• 0.369 sec

• 0.693 sec

What is the time constant of a series RL circuit?

• R/L

• L/R

• RL

• 1/RL

In an RL circuit having a source voltage of 100 V, the resistance is 400 ohms and the inductance is 20 H. What is the time constant?

• 20

• 0.05

• 0.2

• 0.25

A series RL circuit with R = 50 ohms and L = 10 H has a constant voltage E = 100v applied at t = 0 by the closing of a switch. Find the time at which VR = VL

• 0.6931 sec

• 0.1386 sec

• 2.3026 sec

• 0.2773 sec

The field winding of a separately-excited dc generator has an inductance of 60 H and a resistance of 30 ohms. The discharge resistance of 50 ohms is permanently connected in parallel with the winding which is excited from a 200 V supply Find the value of the decay current 0.6 sec after the supply has been switched off

• 4 A

• 3 A

• 2 A

• 1 A

A coil of 10 H inductance and 5 ohms resistance are connected in parallel with 20 ohms resistor across 100 V dc supply which is suddenly disconnected The voltage across the switch contacts at the instant of separation is,

• 500 V

• 400 V

• 300 V

• zero

A capacitor of 8 μF is to be charged by a voltage of 400 v through a resistor of 100 Kohms. How long will it takes for the voltage across the capacitor from its initial zero value to reach 300 v?

• 1.05

• 1.10

• 0.99

• 1.00

A series circuit with 10-ohm resistor and 50 uF capacitor is suddenly connected to a dc source of 120 volts. What is the current at one time constant?

• 12 A

• 2.44 A

• 7.6 A

• 4.4 A

A 200 microfarad capacitor is connected in series with a 10 resistor. The circuit is connected to a 24 v battery. What is the initial current when putting the switch on?

• 1.2 A

• 2.4 A

• 0.225 A

• 0.0125 A

A certain precision 1 microfarad capacitor has very high resistance material used between its conducting surface. The capacitor is charged to 1 volt at t = 0 and disconnected from the source. It is found that the voltage drops to 0.80 v in 1 hour. What is the insulator resistance?

• 24 G ohms

• 24 G ohms

• 16 G ohms

• 12 G ohms