ELECTRICAL ENGINEERS PRE-BOARD EXAMINATION AUGUST 2013

To reverse the direction of rotation of a three-phase induction motor, it is necessary to

• Interchange all the three line connections

• Reverse the polarity of the rotor circuit

• Increase the resistance of the rotor circuit

• Interchange any two of the three line connections

Transformers are rated in

• KW

• KV

• KWHR

• KVA

In a series RL circuit, the inductor current _________ the resistor current.

• Lags

• leads

• is equal to

• is negative of

The power factor of incandescent bulb is

• 0.8 lagging

• 0.8 leading

• unity

• zero

The law that induces emf and current always opposes the cause producing them was discovered by

• Lenz

• Maxwell

• Faraday

• Ohm

Temperature coefficient of a conductor is defined as the

• increase in resistance per ohm per degree centigrade

• increase in resistance per degree centigrade

• increase in resistance per degree absolute

• decrease in resistance per ohm per degree centigrade

Open conductors run individually as service drops shall be _______.

I. insulted II. bare III. covered

• I only

• II only

• III only

• either I or II

The power factor of an alternator is determined by its

• speed

• load

• excitation

• prime mover

The speed of a synchronous motor

• reduces as load increases

• increases as load increases

• adjusts itself to new equilibrium speed whenever load changes

• always remains constant

The efficiency of thermal power plant is approximately

• 10%

• 30%

• 60%

• 80%