40 Questions
What is the unit for current?
Amps (A)
How should an ammeter be connected in a circuit to measure current?
In series
What should be avoided to prevent short-circuit currents in an ammeter?
Connecting in parallel
What is the unit for voltage?
Volts (V)
How should a voltmeter be connected to measure potential difference?
Between two points at different potentials
Why is it crucial to always connect a voltmeter in parallel in a circuit?
To minimize the loading effect and improve accuracy of the reading
Which type of instrument uses an iron plate that moves in response to the magnetic field of the stationary coil?
Moving Iron Instrument
What is the main advantage of a Moving Iron Instrument over other types of instruments?
Universal use for both AC and DC
In a repulsion type instrument, why does the moving coil start moving away from the fixed vane?
Due to force of repulsion between the vanes
What is a disadvantage of the scale of moving iron instruments?
Non-uniform scale leading to inaccurate readings
What is the primary difference between AC and DC calibration of instruments?
The calibration frequency
What is the purpose of the fixed coil in the electrodynamometer wattmeter?
To produce a uniform electric field
Why is a spring control system used in the electrodynamometer wattmeter?
To facilitate pointer movement
What prevents the use of other types of damping in the electrodynamometer wattmeter system?
Destruction of magnetic flux
Which factor can create serious errors in a dynamometer wattmeter at low power factors?
Stray magnetic fields
What is the material used for designing the moving coil in a PMMC instrument?
Aluminum
Which material is used for the permanent magnets in a PMMC instrument?
Alnico
What produces the damping torque in a PMMC instrument?
Eddy Current
What opposes the deflecting torque in a PMMC instrument at steady-state conditions?
Control Spring
Which part of the PMMC instrument indicates the measured current value?
Pointer
What are some advantages of PMMC instruments?
Consumes low power
What does earthing in electrical systems help to protect against?
Electric shock
Why is the body of electrical equipment connected to earth instead of the supply neutral?
Due to limited availability of neutral wire
What is a method of earthing mentioned in the text?
Copper wire plate earthing
What necessity led to the development of electrical earthing?
Protecting personnel from electric shock
What is the purpose of the Braking System in an energy meter?
To reduce the rotation of the aluminium disc
What material is the core of the electromagnet in the Driving System made of?
Silicon steel lamination
Which main part of the energy meter is responsible for recording the number of rotations of the disc?
Registration (Counting Mechanism)
What happens to the aluminium disc in the Moving System when power is consumed by the device?
It starts rotating
In the context of energy meters, what does PMMC stand for?
Permanent Magnet Moving Coil
What is the purpose of embedding the plate in alternate layers of coal and salt for a thickness of 15 cm?
To decrease the resistance value
Why is water poured around the earth electrode in plate earthing?
To increase the efficiency of the earthing system
What is the benefit of placing the GI iron pipe vertically at a depth of 4.75m in pipe earthing?
To decrease resistance
What is one electrical safety precaution mentioned in the text?
Using insulated tools while working
What is the danger of working on receptacles with wet hands?
It increases the conductivity of electric current
What is recommended to do in case of accidental contact with a live wire?
Switch off the main switch and provide non-conducting support
How can the danger of accidental shock be reduced according to the text?
Properly earthing all electrical appliances
What is NOT a recommended practice during electrical work based on the text?
Handle electrical appliances with wet hands
Why should all electric connections at switches, plugs, sockets, and junctions be tight?
To prevent electrical accidents
What should be done immediately in case of short-circuiting or accidental contact with live wires?
Switch off the main switch and provide non-conducting support
Learn about current as the rate of electric charge flow, and voltage as the force driving electric current. Understand how to measure current using ammeters in circuits.
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