1. 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 a field for the generator as well as the ohmmeter.
2. 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.
3. . 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.
4. 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.
5. The role of the compensating coil in a megger is ________
a) reduce current
b) increase voltage
c) control temperature
d) scaling
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.
6. Why is the scale of a megger calibrated in megaohms?
a) to indicate resistance
b) to minimise the current flow
c) to increase the voltage drop
d) to reduce the temperature
Explanation: Current flow through the circuit depends on the magnitude of the e.m.f source. In order to indicate the resistance value indicated by the pointer, the scale of a megger is calibrated.
7. Megger can be used for verifying the electrical insulation level of ____________
a) passive components such as resistance, capacitor and inductance
b) devices such as motor, cable, etc
c) solid state devices
d) liquid crystal devices
Explanation: Solid state devices consist of power electronic components and drives. One of the applications of a Megger circuit is in verifying the electrical insulation levels of devices such as motor, cable, generator, etc.
8. Continuity between any two points can be measured using _________
a) ammeter
b) voltmeter
c) megger
d) galvanometer
Explanation: A galvanometer is used for detecting the balance condition in a bridge circuit. An ammeter measures the current flow through the circuit while the voltmeter is used for determining the voltage across the bridge circuit. A megger circuit can be used to determine the continuity between any two points
9. Electrical continuity between any two points exists if _________
a) there is current flow through them
b) there is a wire connecting the points
c) there is sufficient voltage drop
d) pointer shows deflection
Explanation: Voltage drop across the circuit is measured by using a voltmeter. When the pointer displays full deflection, then there is an electrical continuity between the two points.
10. Megger is also known as _________
a) megohmmeter
b) multimeter
c) galvanometer
d) ammeter
Explanation: A galvanometer is used to detect the balance condition. A multimeter can be used for measurement of voltage, current, resistance and power. A megger is also known as a megohmmeter as it is used for the measurement of resistances in the order of Mῼ.