30 Questions
What is the result of summing the currents at node N from Kirchhoff's law?
The sum of currents at node N is zero
In a delta-connected system, where are the current coils of the wattmeters connected?
In lines R and B
What is the purpose of using instrument transformers in measurement?
To extend the range of the measuring instrument
What type of instrument transformer is used to increase the voltage ranges?
Voltage or potential transformer or PT
What is the advantage of using instrument transformers over shunt and multipliers?
They are used to extend the range of the measuring instrument
What is the total power consumed by the load equal to in a delta-connected system?
The sum of the two wattmeter readings
What is the primary current rating of a CT with a nameplate rating of 500/1 A?
500 A
What is the purpose of the magnetizing current IM in a CT?
To produce flux in the core
What happens when a CT core becomes saturated?
The flux density no longer remains a linear function of the magnetizing force
Why should a CT never have its secondary terminals open-circuited?
To prevent damage to the CT
What is the rated secondary burden of a CT with a nameplate rating of 500/1 A 5 VA 5P20?
5 VA
What is the significance of '5P20' in a CT nameplate rating of 500/1 A 5 VA 5P20?
The CT can carry up to 20 times the rated current
What is the primary difference between a normal power transformer and a current transformer?
The primary winding of a CT is connected in series with the main load
What happens to the flux in the core when the secondary winding gets open circuited?
The flux in the core increases greatly
Why is it important to keep the secondary circuit closed when the primary circuit is energized?
To prevent high voltage from building up in the secondary winding
What happens to the secondary current when the secondary circuit is open circuited?
The secondary reverse mmf vanishes
What is the term for the flux created in the core when the secondary winding is open circuited?
High flux density
What is the essential difference between a potential transformer (PT) and a power transformer?
There is essentially no difference in theory
What is a major consideration when designing shunts for extending the range of ammeters in AC circuits?
The reactance and resistance proportions of the shunt and the meter
What is a limitation of using shunts in AC circuits?
They can cause power loss in the shunt itself
What is a benefit of using instrument transformers in AC circuits?
They can help in reducing overall cost
Why is one terminal of the CT normally earthed?
To prevent accidental damage to the operating personnel
What is the purpose of the primary winding of a CT?
To connect in series with the line carrying the main current
What is the advantage of using a multi-range CT or PT with a single range instrument?
It can be used to cover a wide range of measurement
What is the purpose of the calibrated, compensated attenuator in measuring ac voltage?
To reduce the input voltage to a suitable level
What is the typical voltage drop across an internal calibrated shunt in a digital multimeter?
200 mV
What is an advantage of analog multimeters over digital multimeters?
Portability due to no external power supply
What is a limitation of digital multimeters compared to analog multimeters?
More affected by electronic noise
What is a feature of digital multimeters that allows for further analysis of measurements?
Interface with external equipment
What is a characteristic of digital multimeters compared to analog multimeters?
Smaller in size
This quiz covers the process of measuring AC and DC quantities using digital voltmeters, including the conversion of AC voltage to equivalent DC voltage and the role of attenuators, rectifiers, and filters.
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