Electrical Engineering Quiz

The 3-phase magnetic fields that rise and fall at the same frequency as the supply rotate at the

• synchronous speed

• rotating speed

• magnetic velocity

• torque

Within the rotating magnetic field, the magnetic field of each winding are split by

• 60°

• 180°

• 120°

• 90°

A three phase squirrel cage induction motor consists of

• rotor and field windings

• rotor winding only

• no windings

• field windings only

Which of the following is the correct formula for a force on a current carrying conductor in a magnetic field?

• F = BIA

• F = ABL

• F = BIL

• F = BAL

A conductor of length 0.25m and carrying a current of 2A is placed within a magnetic field of 3.5T. The force acting on the conductor is?

• 17.5 N

• 1.75 N

• 1.75N

• 0.175N

In a single phase, split phase induction the centrifugal switch is connected in

• Parallel with the start winding

• Series with the start winding

• Parallel with the run winding

• Series with the run winding

A squirrel cage induction motor has a three phase supply connected to

• the main field windings only

• the rotor and field windings

• the rotor windings only

• the stator

In the construction of a squirrel cage rotor the rotor conducting bars are

• disconnected at the ends

• shorted at the ends by copper rings

• shorted at the ends by aluminium rings

• Shorted at the ends by non-conducting rings

In a single phase motor the centrifugal switch is used for

• Switching a capacitor into a circuit when the supply is switched on

• Switching a start winding into a circuit when the supply is switched on

• Switching a capacitor out of a circuit when the motor reaches near full speed

• Switching a start winding into a circuit when the supply is switched off

The purpose of the fans around the outer casing of a motor is

• To reduce magnetic losses

• To cool the motor

• To reduce eddy currents

• To increase power