This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Megger”.
1. High resistances are of the order of __________
a) 0.1 Mῼ
b) 10 mῼ
c) 1 kῼ
d) 10 Gῼ
Explanation: Resistances of the order of 0.1 Mῼ and above are known as high resistances. Resistance values upto 1 ῼ are known as low resistances. Resistances upto a few kῼ are known as medium resistances.
2. Megger is a ________
a) source of e.m.f
b) source to measure high resistance
c) type of a null detector
d) current carrier
Explanation: Megger is a portable instrument to measure high resistances.
3. Megger is also used for ________
a) providing additional e.m.f
b) bridge balance
c) testing insulation resistance
d) controlling the temperature
Explanation: A null detector is used to balance the bridge. Additional e.m.f can be provided to a circuit by increasing the magnitude of the voltage source. Megger is used for testing the insulation resistance of cables.
4. Megger works on the principle of ________
a) kirchhoff’s current laws
b) ohm’s law
c) gauss’s law
d) electromagnetic induction
Explanation: Ohm’s law is applicable to only purely resistive circuits which are based on linearity principle. Megger basically works on the principle of electromagnetic induction.
5. The role of the permanent magnet in a megger is to ________
a) provide field
b) provide voltage
c) generate power
d) balance the circuit
Explanation: Voltage can be provided by means of an e.m.f source. Power generation occurs when current flows through a circuit. Permanent magnet in a megger is used to provide field for the generator as well as the ohmmeter.
6. A guard ring is provided in a megger to ________
a) protect the circuit
b) eliminate error
c) reduce current flow
d) limit the temperature rise
Explanation: Temperature rise can be prevented by reducing the flow of excessive current through the circuit. The role of a guard ring in a megger is to reduce the errors due to leakage current.
7. The supply to the megger is given by ________
a) ac motor
b) ac generator
c) permanent magnet dc motor
d) dc generator
Explanation: Megger works on the principle of electromagnetic induction. Supply can be given through a dc motor. A permanent magnet dc motor driven by hand is used as a source of supply to the megger.
8. The moving element of the ohmmeter in a megger consists of ________
a) 1 coil
b) 4 coils
c) 3 coils
d) 10 coils
Explanation: The moving element of an ohmmeter in a megger consists of three coils, namely current or deflection coil, pressure or control coil and compensating coil.
9. The role of the compensating coil in a megger is ________
a) reduce current
b) increase voltage
c) control temperature
Explanation: Temperature is controlled by minimising the flow of current through the circuit. Better scaling proportions can be achieved in a megger by making use of a compensating coil.
Sanfoundry Global Education & Learning Series – Electrical Measurements.
To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.