1. The application of a megger is _________
a) to measure resistance
b) to test for leakage
c) to limit the current
d) to increase the emf of the circuit
Explanation: Current flow through a circuit depends on the magnitude of the voltage source. Magnitude of the voltage source can be increased. A megger is mainly used for testing electrical leakages in wires
2. What is the significance of a megger with respect to high resistance?
a) it is used to limit the current
b) it is used to provide stability
c) used for measuring high resistance with respect to ground
d) it is used for temperature protection
Explanation: Temperature protection can be provided to a bridge circuit by making use of heat sinks. Megger is used for determining very high resistances between the conducting part of a circuit and ground.
3. How is the megger calibrated?
a) in steps of 1 unit per division
b) based on the value of resistance to be measured
c) directly calibrated on the position of the pointer
d) reversely calibrated based on the pointer position
Explanation:The scale in a megger is calibrated such that normal position of a pointer indicates infinity while full scale corresponds to zero resistance.
4. What is earthing?
a) connecting electrical machines to earth
b) providing a connection to the ground
c) connecting the electrical machines to source
d) providing a source of current
Explanation: Connecting electrical machines to the general mass of the earth by making use of a conducting material with very low resistance is known as earthing
5. What is an earth electrode?
a) electrode that is connected to earth
b) material used for earthing
c) electrode connected to the circuit
d) electrode which is connected to the mains
Explanation: Electrode connected to the main is basically a source of e.m.f. Conducting material that is used for connecting electrical machinery to the earth is known as an earth electrode.
6. Earth electrode provides ____________
a) high resistance
b) medium resistance
c) low resistance
d) very high resistance
Explanation: In the case of occurrence of any leakage currents due to poor shielding of the apparatus, the earth electrode is used to provide a very low resistance path from the electrical appliances to the earth.
7. How is the condition of an earth electrode measured?
a) by measuring the voltage
b) by measuring the current
c) by measuring the power
d) by measuring resistance
Explanation: The resistance of the earth electrode is measured in order to check whether it is in a good condition or not
8. In a three phase system, the neutral is _________
a) earthed
b) connected to low voltage
c) connected to high voltage
d) not connected
Explanation: Earthing can be used to maintain a constant line voltage in a three phase system. This is achieved by earthing the neutral.
9. Earthing is used as return conductor in telephone lines and for traction work.
a) True
b) False
Explanation: The complications involved in laying separate telephone cables and the cast used for traction work is minimised. As a result earthing is used as a return conductor in telephone lines and for traction work.
10. Earthing does not help in protecting the equipment.
a) True
b) False
Explanation: Spike voltages occurring as a result of lightning or any other fault can be dissipated to ground by earthing, thus protecting the equipment.