This Portion of Electrical andElectronic Measurements and Measuring instruments contains Measurement of Power and Wattmeter MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.

This Section covers below lists of topics.

1. Power in D.C Circuits
2. Power in A.C Circuits
3. Electrodynamometer Wattmeters
4. Ferrodynamic Wattmeters
5. Low Power Factor Wattmeters
6. Thermocouple Wattmeters
7. Hall Effect Multiplier
8. Measurement of power using instrument transformers
9. Power in polyphase System
10. Measurement of power in Three phase circuits
11. Three phase Wattmeters
12. Measurement of Reactive Power

PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE

#### 1. The power in a d.c circuit is measured with the help of ammeter and a voltmeter. The voltmeter is connected on the load side.the power indicated by the product of reading of two instruments (VI) is :

• The power consumed in the load
• The sum of power consumed by the load and the voltmeter
• The sum of power consumed by the load and ammeter
• None of the above.

#### 2. In an electrodynamometer type of wattmeter :

• The current coil is made fixed
• The pressure coil is fixed
• Any of the two coil i.e current coil or pressure coil can be made fixed
• Both the coil should be movable

#### 3. In electrodynamometer type wattmeters, current coils designed for carrying heavy currents use stranded wire or laminated conductors :

• To reduce iron losses
• To reduce hysteresis losses
• To reduce eddy current losses in conductors
• All the above.

#### 4. In electrodynamometer type of wattmeters , the inductance of pressure coil  circuit produces error

• Which is constant irrespective of the power factor of the load
• Which is higher at low power factors
• Which is lower at low power factors
• None of the above.

• 0.41L/r2
• 0.41L/(Rp)2
• L/(Rp)2
• L/r2

#### 6. when measuring power with the electrodynamometer wattmeter in a circuit where the load current is small

• the current coil should be connected on the load side
• the pressure coil should be connected on the load side
• it is immaterial whether current coil or pressure coil is connected on the load side.
• None of the above.

#### 7. when measuring power with the electrodynamometer wattmeter in a circuit where the load current is large

• the current coil should be connected on the load side
• the pressure coil should be connected on the load side
• it is immaterial whether current coil or pressure coil is connected on the load side.
• none of the above.

#### 8. when measuring power with the electrodynamometer wattmeter in a circuit having a low power factor :

• the current coil should be connected on the load side
• the current coil should be connected on the supply side
• the pressure coil should be connected on the load side
• a compensated wattmeter with pressure coil connected on the load side should be used.

• 2 wattmeters
• 4 wattmeters
• 3 wattmeters
• 1 wattmeters

#### 10. The power in 3 phase circuit is measured with the help of 2 wattmeters. The reading of the one of the wattmeters is positive and that of the other is negative. The magnitude of reading is different. it can concluded that the power factor of the circuit is :

• Unity
• Zero (lagging)
• 0.5 (lagging)
• Less than 0.5 (lagging)

#### 11. Power consumed by a simple dc circuit can be measured with the help of a single ammeter if

• the load resistance is known
• the supply voltage is known
• both of (a) and (b) known
• cannot be measured

#### 12. Power indicated while measuring power in a dc circuit using an ammeter and a voltmeter, when the voltmeter is connected to the load side, is

• true power consumed by the load
• power consumed by the load plus power lost in ammeter
• power consumed by the load plus power lost in voltmeter
• power consumed by load plus power lost in both ammeter and voltmeter

#### 13. In ammeter–voltmeter method for measurement of power in dc circuits, true power will be obtained with ammeter connected to the load side when

• voltmeter has zero internal impedance
• ammeter has zero internal impedance
• ammeter has infinite internal impedance
• voltmeter has infinite internal impedance

#### 14. Electrodynamometer-type wattmeters have a construction where

• current coil is fixed
• voltage coil is fixed
• both voltage and current coils are movable
• both voltage and current coils are fixed

#### 15. In electrodynamometer-type wattmeters, current coil is made of two sections

• to reduce power loss
• to produce uniform magnetic field
• to prevent Eddy-current loss
• to reduce errors due to stray magnetic field

#### 16. In electrodynamometer-type wattmeters, current coils carrying heavy currents are made of stranded wire

• to reduce iron loss
• to reduce Eddy-current loss in conductor
• to reduce hysteresis loss
• all of the above

#### 17. In electrodynamometer-type wattmeters, a high value noninductive resistance is connected in series with the pressure coil

• to prevent overheating of the spring leading current in the pressure coil
• to restrict the current in the pressure coil
• to improve power factor of the pressure coil
• all of the above

#### 18. In electrodynamometer-type wattmeters, both current coil and pressure coil are preferably air-cored

• to reduce effects of stray magnetic field
• to reduce Eddy-current losses under AC operation
• to increase the deflecting torque
• all of the above

#### 19. In electrodynamometer-type wattmeters, pressure coil inductance produce error which is

• constant irrespective of load power factor
• higher at low power factors of load
• lower at low power factors of load

#### 20. When measuring power in a circuit with low current, the wattmeter current coil should be connected

• to the source side
• anywhere, either load side or source side, does not matter
• in series with the load along with CT for current amplification

#### 21. When measuring power in a circuit with high current

• current coil should be connected to the load side
• pressure coil should be connected to the load side
• pressure coil should be connected to the source side
• the placement of pressure and current coils are immaterial

#### 22. In induction-type wattmeters,

• voltage coil is the moving coil
• current coil is the moving coil
• both are moving
• none are moving

#### 23. Three wattmeters are used to measure power in a 3-phase balanced star connected load.

• The reading will be higher when the neutral point is used as the common point for wattmeter pressure coils.
• The reading will be lower when the neutral point is used as the common point for wattmeter pressure coils.
• Wattmeter reading will remain unchanged irrespective whether the neutral is used for measurement or not.
• The three-wattmeter method cannot be used in systems with 4 wires.