WorksheetsUNIT 4 :ELECTRICAL MACHINES
Total questions: 10
Worksheet time: 5mins
A DC machine works on the principle of:
Mutual induction
Faraday’s law of electromagnetic induction
Static induction
Reluctance force
In a DC generator, EMF is developed due to:
Conductors moving in a magnetic field
Voltage drop in armature
Eddy currents
Commutator action
The EMF equation of a DC generator is:
E = 2πNΦ
E = (PΦZN) / (60A)
E = 4.44 f N Φ
E = V/R
A DC shunt motor has:
Field winding in series with armature
Field winding in parallel with armature
No field winding
Variable field resistance only
The speed–torque characteristic of a DC shunt motor is:
Nearly constant speed
Drooping speed
Increasing speed
No-load runaway
A 3-phase induction motor works on the principle of:
Eddy currents
Lenz law only
Production of rotating magnetic field
Static magnetic field
Slip in an induction motor is defined as:
(Ns – N) / N
(Ns – N) / Ns
(N – Ns) / N
N / Ns
What is the torque–slip characteristic?
LOW Slip
HIGH Slip
BOTH
Slip = infinite
A synchronous generator works on the principle of:
Rotating magnetic field
Faraday’s law – relative motion between field & conductors
Torque–angle
Magnetic reluctance
The speed of a synchronous generator is:
Dependent on load
Slightly varies with slip
Constant & f=PN/120
Equal to rotor frequency
