MCQOPTIONS
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MCQOPTIONS
This section includes 37 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In 'two-wattmeter method' of power calculation of a 3-phase balanced star connected system, what is the power factor of the system if both the wattmeter’s show a positive reading? |
| A. | 0 |
| B. | Greater than 0 but less than 0.5 |
| C. | 3.5 |
| D. | Greater than 0.5 but less than 1 |
| Answer» E. | |
| 2. |
A 3-phase 10 kVA load has a power factor of 0.342. The power is measured by the two-wattmeter method.Find the reading of each wattmeter when the power factor is leading. |
| A. | W1 = -1 kW and W2 = 4.4 kW |
| B. | W1 = -4.4 kW and W2 = 1 kW |
| C. | W1 = 1 kW and W2 = 4.4 kW |
| D. | W1 = 4.4 kW and W2 = 1 kW |
| Answer» B. W1 = -4.4 kW and W2 = 1 kW | |
| 3. |
In two wattmeter method of power calculation of a 3-phase balanced star connected system, what is the power factor of the system, if both the wattmeters show the same positive reading? |
| A. | 0 |
| B. | Greater than 0 but less than 0.5 |
| C. | Greater than 0.5 but less than 1 |
| D. | 1 |
| Answer» E. | |
| 4. |
A device capable of detecting voltage, current and the angle between the voltage and the current to provide power readings directly in watts is known as a/an: |
| A. | ammeter |
| B. | wattmeter |
| C. | power factor meter |
| D. | voltmeter |
| Answer» C. power factor meter | |
| 5. |
A balanced 3-phase star-connected load draws power from a 440 V supply. The two watt-meters connected indicate W1 = 4.2 kW and W2 = 0.8 kW. Calculate the current in the circuit in Amperes |
| A. | 10.731 |
| B. | 10.137 |
| C. | 10.271 |
| D. | 10.371 |
| Answer» C. 10.271 | |
| 6. |
For a balanced load, the reactive power is measured by two wattmeter method with readings W1 and W2, the total reactive power is given by: |
| A. | (W1 – W2) |
| B. | (W1 + W2) |
| C. | √3 (W1 + W2) |
| D. | √3 (W1 – W2) |
| Answer» E. | |
| 7. |
In a crossed coil power factor meter the moving coils should be mounted on which type of shaft and at what angles to each other? |
| A. | Different shafts and right angles |
| B. | Same shaft and right angles |
| C. | Different shafts and 45° angles |
| D. | same shaft and 45° angels |
| Answer» C. Different shafts and 45° angles | |
| 8. |
A three-phase 10 kVA load has a power factor of 0.342. The power is measured by the two-wattmeter method.Find the reading of each wattmeter when the power factor is lagging. |
| A. | W1 = 1 kW and W2 = 4.4 kW |
| B. | W1 = -1 kW and W2 = -4.4 kW |
| C. | W1 = 4.4 kW and W2 = -1 kW |
| D. | W1 = -4.4 kW and W2 = 1 kW |
| Answer» D. W1 = -4.4 kW and W2 = 1 kW | |
| 9. |
For a delta-connected load being measured for power by the two-wattmeter method, if Iph will lead Vph by angle ϕ then it is the case of __________. |
| A. | Short circuit |
| B. | Leading power factor |
| C. | Lagging power factor |
| D. | Open circuit |
| Answer» C. Lagging power factor | |
| 10. |
A dynamometer instrument is mainly used as |
| A. | dc ammeter |
| B. | wattmeter |
| C. | dc voltmeter |
| D. | ohmmeter |
| Answer» C. dc voltmeter | |
| 11. |
In the two-wattmeter method, the readings of the two wattmeters are 500 W, 500 W respectively. The load power factor in a balanced 3-phase 3-wire circuit is: |
| A. | 0.8 |
| B. | 0 |
| C. | 1 |
| D. | 0.3 |
| Answer» D. 0.3 | |
| 12. |
In case of the two-wattmeter method for measuring the power of a balanced 3ϕ load, the whole power is measured by one of the two wattmeters when: |
| A. | The power factor is unity |
| B. | The power factor is more than 0.5 but less than 1 |
| C. | The power factor is 0.5 |
| D. | The power factor is less than 0.5 but more than 0 |
| Answer» D. The power factor is less than 0.5 but more than 0 | |
| 13. |
A delta-connected balanced load is supplied from a three-phase balanced 400 V, 50 Hz AC supply. The reading on the two wattmeters is 970 W and 480 W respectively. Each phase of the load consists of resistance and inductance connected in series. Calculate the total active power consumed. |
| A. | 14.5 kW |
| B. | 1,450 kW |
| C. | 1.45 kW |
| D. | 145 kW |
| Answer» D. 145 kW | |
| 14. |
In a two-wattmeter measurement of power in a three-phase circuit, both the wattmeters show equal readings. In this case, the load power factor is: |
| A. | Zero |
| B. | Unity |
| C. | 0.8 Lagging |
| D. | 0.8 Leadings |
| Answer» C. 0.8 Lagging | |
| 15. |
In the two-wattmeter method of 3ϕ power measurement, if the phase sequence of the supply is reversed: |
| A. | one of the meters will show a negative reading |
| B. | the meters will not read |
| C. | there won't be a change in meter readings |
| D. | the reading of wattmeters will be interchanged |
| Answer» E. | |
| 16. |
If two watt-meters used to measure three phase power read equal reading, then the power factor is: |
| A. | 0.866 |
| B. | 0.5 |
| C. | 0 |
| D. | 1 |
| Answer» E. | |
| 17. |
________ is a measuring device which can evaluate and record the electrical power passing through a circuit in a certain time.By implementing it, we can know how much amount of electrical energy is used by a consumer or a residence or an electrically powered device or a business. |
| A. | DC meter |
| B. | Air flow meter |
| C. | Watt hour meter |
| D. | AC meter |
| Answer» D. AC meter | |
| 18. |
In ‘Two-wattmeter method’ of power calculation of a 3-phase balanced star connected system, what is the power factor of the system, if one of the wattmeter’s shows negative reading and the other shows a positive reading? |
| A. | Greater than or equal 0 but less than 0.5 |
| B. | 0.5 |
| C. | Greater than 0.5 but less than equal to 1 |
| D. | Greater than 1 |
| Answer» B. 0.5 | |
| 19. |
In a low power factor wattmeter, sometimes compensating coil is connected in order to |
| A. | neutralize the capacitive effect of pressure coil |
| B. | compensate for inductance of pressure coil |
| C. | compensate for power loss in the pressure coil |
| D. | reduce the error caused by eddy current |
| Answer» D. reduce the error caused by eddy current | |
| 20. |
For balanced lagging power factor, according to two wattmeter method,W1 = VL IL cos (30 - ϕ)W2 = VL IL cos (30 + ϕ)The total reactive volt-amperes Q is given by |
| A. | Q = 0 |
| B. | Q = \(\sqrt 3 {V_L}{I_L}\sin \phi\) |
| C. | Q = 1 |
| D. | Q = VLILsin ϕ |
| Answer» C. Q = 1 | |
| 21. |
A 3 phase – 110 V motor has a power factor of 0.5. The two watt-meters connected measure the total input of 50 kW. Calculate the reading (in kW) of each wattmeter. |
| A. | 0, 150 |
| B. | 100, 50 |
| C. | 0, 50 |
| D. | 50, 50 |
| Answer» D. 50, 50 | |
| 22. |
For a delta-connected load being measured for power by the two-wattmeter method, if W1 = VLIL cos (30 - ϕ) and W2 = VLIL cos (30 + ϕ), Then total 3-phase power is: |
| A. | \(\sqrt 3 {V_L}{I_L}\cos \phi \) |
| B. | \(\sqrt 3 {V_{ph}}{I_{ph}}\cos \left( {30 + \phi } \right)\) |
| C. | \(3{V_{ph}}{I_{ph}}\sin \left( {30 + \phi } \right)\) |
| D. | \(\sqrt 3 {V_L}{I_L}\sin \left( {30 + \phi } \right)\) |
| Answer» B. \(\sqrt 3 {V_{ph}}{I_{ph}}\cos \left( {30 + \phi } \right)\) | |
| 23. |
Electric heater utilizes __________ effect of current. |
| A. | Chemical |
| B. | Heating |
| C. | Mechanical |
| D. | Filed |
| Answer» C. Mechanical | |
| 24. |
According to Blondel’s theorem, if a network is supplied using ‘n’ conductor’s the total power is ________ of the reading of n wattmeter’s so arranged that a current coil of each wattmeter is in each line and the corresponding pressure coil is connected between that line and a common point |
| A. | Sum |
| B. | Product |
| C. | Sum of products of two wattmeter’s reading taken together |
| D. | Difference |
| Answer» B. Product | |
| 25. |
In 3ϕ power measurement for a balanced load using the two-wattmeter method, the reactive power is given by: |
| A. | the sum of both the wattmeter readings |
| B. | √2 times the difference of the readings of the two wattmeters |
| C. | √3 times the sum of the readings of the two wattmeters |
| D. | √3 times the difference of the readings of the two wattmeters |
| Answer» E. | |
| 26. |
A balanced three-phase star-connected load draws power from a 440V supply. The two connected wattmeters’, W1 and W2, indicate 5 kW and 1,200 W respectively. Calculate the current in the circuit. |
| A. | 11.86 A |
| B. | 15.56 A |
| C. | 1.11 A |
| D. | 10.11 A |
| Answer» B. 15.56 A | |
| 27. |
Phase voltage and current of a 3ϕ, three-wire star-connected system, with an inductive load of power factor 0.707 (lag), is 150 V and \(30\sqrt 3 {\rm{A}}\). If the power in the system is being measured using two wattmeter’s, the difference in meter readings is: |
| A. | 10.46 KW |
| B. | 2.26 KW |
| C. | 3.95 KW |
| D. | 9.54 KW |
| Answer» E. | |
| 28. |
In the two-wattmeter method of three phase power measurement of a balanced load, if the reading of one metre is – 200 W, then then power factor of the load is ______. |
| A. | greater than 0.5 |
| B. | less than 0.5 |
| C. | equal to 0.5 |
| D. | equal to zero |
| Answer» C. equal to 0.5 | |
| 29. |
A 3-phase balanced supply system is connected to a 3-phase unbalanced load. Power supplied to this load can be measured using:1. two wattmeters2. one wattmeter3. three wattmetersWhich of these statement/s is/are correct? |
| A. | 1 and 2 |
| B. | 1 and 3 |
| C. | 2 and 3 |
| D. | 3 alone |
| Answer» C. 2 and 3 | |
| 30. |
Baretters and Bolometers are used for measurement of |
| A. | VSWR |
| B. | Transmission losses |
| C. | Microwave power |
| D. | None of the above |
| Answer» D. None of the above | |
| 31. |
A balanced three-phase star-connected load draws power from a 440 V supply. The two connected wattmeters W1 and W2, indicate 5 kW and 1200 W. Calculate the total power. |
| A. | 5 kW |
| B. | 6,200 kW |
| C. | 62 kW |
| D. | 6,200 W |
| Answer» E. | |
| 32. |
For a star-connected load being measured for power by the two-wattmeter method, if W1 = VLIL cos (30 - ϕ) and W2 = VLIL cos (30 + ϕ), then the total 3-phase power will be: |
| A. | \(3{V_{ph}}{I_{ph}}\sin \left( \phi \right)\) |
| B. | \(\sqrt 3 {V_L}{I_L}\cos \left( \phi \right)\) |
| C. | \(\sqrt 3 {V_{ph}}{I_{ph}}\sin \left( {30 + \phi } \right)\) |
| D. | \(\sqrt 3 {V_L}{I_L}\cos \left( {30 + \phi } \right)\) |
| Answer» C. \(\sqrt 3 {V_{ph}}{I_{ph}}\sin \left( {30 + \phi } \right)\) | |
| 33. |
In the circuit shown, the pressure coils of two wattmeters are connected to: |
| A. | neutral wire |
| B. | B |
| C. | Y |
| D. | R |
| Answer» C. Y | |
| 34. |
A three-phase star-connected balanced load of (4 + j3) Ω per phase is connected across three-phase, 50 Hz, 400 V AC supply. If the two-wattmeter method is used to determine input power, find each wattmeter reading. |
| A. | 18.34 kW and 7.26 kW |
| B. | 18.34 kW and 46 kW |
| C. | 23 kW and 23 kW |
| D. | 25.60 kW and 23.23 kW |
| Answer» B. 18.34 kW and 46 kW | |
| 35. |
One B.O.T. is: |
| A. | 1 kWh |
| B. | 0.1 kWh |
| C. | 0.01 kWh |
| D. | 0.001 kWh |
| Answer» B. 0.1 kWh | |
| 36. |
A wattmeter having a range of 4000 W has an error of ±2% of full-scale deflection. If the true power is 2000 W, what would be the range of the reading? |
| A. | 1920-2000 W |
| B. | 2000-2080 W |
| C. | 1920-2040 W |
| D. | 1920-2080 W |
| Answer» E. | |
| 37. |
A balanced three-phase star-connected load draws power from a 440 V supply. The two connected wattmeters, W1 and W2, Indicate 5 kW and 1,200 W respectively. Calculate the power factor of the system. |
| A. | 0.54 |
| B. | 0.98 |
| C. | 0.69 |
| D. | 0.75 |
| Answer» D. 0.75 | |