40 Questions
What is the symbol for current?
A
How should an ammeter be connected to measure current?
In series with the load
What problem may occur if an ammeter is connected in parallel with a circuit component?
Short-circuit current
What is the unit of voltage?
Volts
Why is it important for ammeters to have low internal resistance?
To not alter the current in the circuit
What causes waveform error in MI instruments?
The effect of inductance on the eddy current
Why is the fixed coil of the electrodynamometer wattmeter split into two parts?
To allow the load current to flow through it
What type of control system does the Electrodynamometer Wattmeter use?
Spring control system
What is the purpose of the knife-edge pointer in electrodynamometer wattmeters?
To eliminate parallax error
What is the major disadvantage of the Dynamometer Type Wattmeter at low power factors?
Errors due to inductance in the potential coil
What is a major advantage of the PMMC instrument?
High torque to weight ratio
Why is the body of the electrical equipment not connected to the supply neutral directly?
Long transmission lines increase resistance
Which application is NOT listed for the PMMC instrument?
Wattmeter
What is the primary purpose of electrical earthing?
To protect equipment from damage
What is a key advantage of plate earthing over pipe earthing?
Lower maintenance
Why is connecting a voltmeter in parallel important in a circuit?
To minimize the loading effect
What is the purpose of the high internal resistance in voltmeters?
To draw as little current from the circuit as possible
How does a repulsion type instrument function in measuring current?
By generating a force of repulsion between two magnetized vanes
Why are moving iron instruments considered robust?
Because of simple construction and stationary current-carrying parts
What is a disadvantage of moving iron instruments in terms of accuracy?
They have a non-uniform scale
What is the purpose of the aluminum former in the PMMC instrument?
To produce damping torque
Which material are the permanent magnets in the PMMC instrument made of?
Alnico
What is the role of the control spring system in the PMMC instrument?
To produce controlling torque
How does the PMMC instrument reach a steady-state position?
Through the action of eddy currents on the aluminum former
What is the role of the mirror and proper alignment of the pointer blade in the PMMC instrument?
To reduce parallax error
What is the main component of the driving system in a single-phase energy meter?
Electromagnet
What is the purpose of the braking system in an energy meter?
To reduce the rotation of the aluminium disc
How is the movement of the aluminium disc controlled in an energy meter?
By shifting the permanent magnet position
What is the role of the register system in an energy meter?
To record the number of disc rotations
What does the PMMC instrument measure in an energy meter?
Current
What is the purpose of pouring water in the Plate Earthing system?
To maintain the earth electrode resistance value below 5 ohms
In Pipe Earthing, why is a mixture of salt and coal filled around the GI pipe?
To keep the value of the earth resistance at the desired level
Why are insulated tools recommended while working with electricity?
To avoid getting a severe shock
Why should all electric connections at switches, plugs, sockets, and junctions be tight?
To reduce the dangers of any accidental shocks
What should be done immediately in the case of a short-circuit or accidental contact with a live wire?
Provide support of non-conducting material
How can you decrease the danger of any accidental shock?
Properly earth all electrical appliances
What is the purpose of avoiding contact with water while working with electricity?
To improve safety
Why must fuses and switches be connected in the live wires?
To reduce the risk of fires
What should be done if a person has accidentally contacted a live wire?
Immediately turn off the main switch
Why is it recommended to use rubber gloves and goggles while working on any electrical circuit?
To ensure personal safety
Learn about current and voltage in electrical circuits, including their symbols, units, and measurement techniques. Discover how to use ammeters to measure current by breaking the circuit at the desired point.
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