Electrician DC machine mini quiz

1➤ Which rule is used to find the direction of induced emf in D.C generator?

Fleming’s left-hand rule Cork screw ruleRight hand palm ruleFleming's right-hand rule

2➤ What is the formula to calculate back emf of a D.C motor?

All of these Eb = V – Ia Ra VoltsEb = V + Ia Ra VoltsEb = V x Ia Ra Volt

3➤ How interpoles are connected in a DC generator?

In series with armature In series with shunt fieldIn parallel with armatureIn parallel with shunt field

4➤ Why the armature core of a DC generator is laminated?

Reduce the copper lossReduce the hysteresis loss Reduce the eddy current lossReduce the friction loss

5➤ Why the D.C generator should run in clockwise direction only?

Avoid short circuit in armature Avoid over loading of generatorProtect brushes from damageProtect the residual magnetism

6➤ What is the function of split rings in DC generator?

Maintain constant voltage Collects the current unidirectionallyBoth A and BEither A or B

7➤ Why DC generators are loosing their residual magnetism?

Change of direction of rotation very oftenContinuous running without break Heavy short circuit in load Running without load continuously

8➤ Which instrument is used to measure armature winding resistance?

Series type Ohm meter Kelvin bridgeMultimeterMegger

9➤ Which instrument is used to test armature winding for short and open circuit?

Internal Growler Tong TesterDigital multimeterExternal Growler

10➤ What is the purpose of series resistor connected with holding coil in a D.C four point starter?

Increase the voltage in holding coilDecrease the voltage in holding coilLimit the current in holding coilIncrease the current in holding coil

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