# Electrical Measurements & Units Test Questions - 5

1)   In MKS system of units, the dimensions of E.M.F is given by

a. [M-1L-1T-2I-1]
b. [ML2T-3I-1]
c. [M2L1T-2I-1]
d. [M1L-1T-2I-1]
 Answer  Explanation  Related Ques ANSWER: [ML2T-3I-1] Explanation: No explanation is available for this question!

2)   The units for inductance and capacitance in terms of MKS units are[M1L-1T-2I-1], [M1L-1T-2I-1]

a. [M1L-1T-2I-1], [M-1L-4T-2I-2]
b. [M1L-2T-2I-1], [M1L-2T-4I2]
c. [M1L2T-2I-2], [M-1L-2T4I2]
d. [M-1L2T-2I-1], [M1L-2T2I1]
 Answer  Explanation  Related Ques ANSWER: [M1L2T-2I-2], [M-1L-2T4I2] Explanation: No explanation is available for this question!

3)   By the surface, the solid angle subtended at the centre of a sphere, whose area is equal to the surface of the radius of the sphere is known as

c. Candela
d. Lux

4)   At the centre, the plane angle subtended by an arc of a circle equal to the radius of the circle is known as

b. Candela
c. Lumen

5)   For an ac series circuit, the resonant frequency is given by, f =1/2πLaCb. The values of a and b will be

a. 2, 2
b. 1/2, ½
c. -1/2, -1/2
d. -1/2,1/2
 Answer  Explanation  Related Ques ANSWER: -1/2, -1/2 Explanation: No explanation is available for this question!

6)   If the energy stored in a parallel plate capacitor in terms of inductance and capacitance is given by, W = KCaVb where K is a constant, then the values of a and b are

a. 1, 1
b. 1, 2
c. 2, 1
d. 1/2, 2/3
 Answer  Explanation  Related Ques ANSWER: 1, 2 Explanation: No explanation is available for this question!

7)   Bridge circuits are used for the measurement of

a. Resistance
b. Inductance
c. Capacitance
d. All of these
 Answer  Explanation  Related Ques ANSWER: All of these Explanation: No explanation is available for this question!

8)   Low resistance is the resistance of the order of

a. 1 ohm and less than 1 ohm
b. 1 ohm to 1 mega ohm
c. More than one ohm
d. None of these
 Answer  Explanation  Related Ques ANSWER: 1 ohm and less than 1 ohm Explanation: No explanation is available for this question!

9)   The example of low resistance is/are

a. Resistance of armature windings of electrical machine
b. Resistance of series field winding of a dc machine
c. Resistances of shunts and lead wires
d. All of these
 Answer  Explanation  Related Ques ANSWER: All of these Explanation: No explanation is available for this question!

10)   The accuracy in a bridge measurement depends on

a. Sensitivity of detector
b. Applied voltage
c. Accuracy of indicator
d. Both (a) and (b)
 Answer  Explanation  Related Ques ANSWER: Both (a) and (b) Explanation: No explanation is available for this question!

11)   The high resistances are found in

a. Insulation resistance of cables and wires
b. Resistance of shunt field winding and the multipliers
c. Resistance of armature windings of electrical machine
d. Resistance of series field winding of a dc machine
 Answer  Explanation  Related Ques ANSWER: Insulation resistance of cables and wires Explanation: No explanation is available for this question!

12)   A null type of bridge with dc excitation is commonly known as

a. Wheatstone bridge
b. Anderson bridge
c. Wien bridge
d. Schering bridge
 Answer  Explanation  Related Ques ANSWER: Wheatstone bridge Explanation: No explanation is available for this question!

13)   In Wheatstone bridge method, the instrument used as null detector is

a. Ammeter
b. Voltmeter
c. Galvanometer
d. All of these
 Answer  Explanation  Related Ques ANSWER: Galvanometer Explanation: No explanation is available for this question!

14)   In a Wheatstone bridge method, the bridge is said to be balanced, when the current through the galvanometer is

a. 1 A
b. 0 A
c. Maximum
d. Half of the maximum value
 Answer  Explanation  Related Ques ANSWER: 0 A Explanation: No explanation is available for this question!

15)   The given figure shows the Wheatstone bridge method for measurement of unknown resistance (R). The balanced equation for Wheatstone bridge is given by

a. P/R = Q/S
b. P/S = Q/R
c. P/R = S/Q
d. R/P = Q/S
 Answer  Explanation  Related Ques ANSWER: P/R = Q/S Explanation: No explanation is available for this question!

16)   The sensitivity of Wheatstone bridge is defined as ratio of

a. Deflection of the galvanometer to the unit fractional change in the value of unknown resistance
b. Square of the deflection of the galvanometer to the unit fractional change in the value of unknown resistance
c. Deflection of the galvanometer to the twice of the unit fractional change in the value of unknown resistance
d. Unit fractional change in the value of unknown resistance to the deflection of the galvanometer
 Answer  Explanation  Related Ques ANSWER: Deflection of the galvanometer to the unit fractional change in the value of unknown resistance Explanation: No explanation is available for this question!

17)   The sensitivity of the bridge is maximum when

a. P/R = Q/S = 0
b. P/R = 1
c. Both (a) and (b)
d. None of these
 Answer  Explanation  Related Ques ANSWER: P/R = 1 Explanation: No explanation is available for this question!

18)   During a test, the strain gauge with resistance of 200 ohm undergoes a change of 0.120 ohm and the strain of the gauge is 1.2 X10-4. Then the gauge factor will be

a. 4
b. 5
c. 4.5
d. 6
 Answer  Explanation  Related Ques ANSWER: 5 Explanation: No explanation is available for this question!

19)   Wheatstone bridge is suitable for the measurement of

a. Low resistance
b. Medium resistance
c. High resistance
d. Very high resistance
 Answer  Explanation  Related Ques ANSWER: Medium resistance Explanation: No explanation is available for this question!

20)   The resistances of the various arms of Wheatstone bridge are P = 500 ohm, Q = 50 ohm, R = 1010 ohm and S = 100 ohm. The emf of the batter is 5 V and the current sensitivity of galvanometer is 8 mm/μA. If the internal resistance of the galvanometer is 80 ohm then the deflection of galvanometer and the sensitivity of the bridge in terms of deflection per unit change of resistance are

a. 151.2 mm, 30.24 mm/ohm
b. 100 mm, 21.03 mm/ohm
c. 186 mm, 40.37 mm/ohm
d. 193 mm, 20.74 mm/ohm
 Answer  Explanation  Related Ques ANSWER: 151.2 mm, 30.24 mm/ohm Explanation: No explanation is available for this question!

21)   To produce a change of 2 mm in deflection of galvanometer, a change of 4 ohm is required in the unknown arm of a Wheatstone bridge. The sensitivity of the galvanometer is

a. 1 mm/ohm
b. 0.5 mm/ohm
c. 1.5 mm/ohm
d. 2 mm/ohm
 Answer  Explanation  Related Ques ANSWER: 0.5 mm/ohm Explanation: No explanation is available for this question!

22)   In a Wheatstone bridge, if P = 10 ± 1%, Q = 100 ± 1%, R = 20 ± 1% and S is unknown then the unknown resistance will be

a. 200 ± 1%
b. 200 ± 2%
c. 200 ± 3%
d. 100 ± 1%
 Answer  Explanation  Related Ques ANSWER: 200 ± 3% Explanation: No explanation is available for this question!

23)   A highly sensitive galvanometer is used in Wheatstone bridge and it can detect a current as low as 80 pA. The resistances of each arm of bridge are 800 ohm and the resistance of galvanometer is 40 ohm. If an input of 20 V is applied to the bridge then the smallest change in resistance which can be detected is

a. 10.752 μA
b. 15.280 μA
c. 17.351 μA
d. 23.719 μA
 Answer  Explanation  Related Ques ANSWER: 10.752 μA Explanation: No explanation is available for this question!

24)   The method/methods suitable for the measurement of low resistance is/are

a. Ammeter-voltmeter method
b. Kelvin’s double bridge method
c. Potentiometer method
d. All of these
 Answer  Explanation  Related Ques ANSWER: All of these Explanation: No explanation is available for this question!

25)   For the measurement of low resistances, Kelvin’s double bridge has high accuracy because

a. It has two set of ratio arms which eliminates effect of resistance of connecting lead
b. It has a null indicating galvanometer
c. It has two null indicator
d. It has four sets of ratio arms which eliminates the effect of resistance of connecting lead
 Answer  Explanation  Related Ques ANSWER: It has two set of ratio arms which eliminates effect of resistance of connecting lead Explanation: No explanation is available for this question!

26)   For the measurement of low resistances from few ohms down to one micro ohm, which of the following instrument is not suitable?

a. Potentiometer method
b. Ammeter –voltmeter method
c. Ohmmeter
d. Kelvin double bridge method
 Answer  Explanation  Related Ques ANSWER: Ohmmeter Explanation: No explanation is available for this question!

27)   In a slide wire potentiometer, for a voltage source of 1.012 V the jockey is kept at 101.2 cm. If the potentiometer has 20 wires of 1 m each and the resistance of wires is 800 ohm, then the value of the working current is

a. 15 mA
b. 20 mA
c. 25 mA
d. 27 mA
 Answer  Explanation  Related Ques ANSWER: 25 mA Explanation: No explanation is available for this question!

28)   When a voltmeter-ammeter method is applied for the measurement of resistance, the voltmeter reads a value of 8.28 V and the ammeter reading is 4.14 mA. Then the value of the resistance will be

a. 2 kΩ
b. 2.0 kΩ
c. 2.00 kΩ
d. 2.000 kΩ
 Answer  Explanation  Related Ques ANSWER: 2.00 kΩ Explanation: No explanation is available for this question!

29)   Electrical equipments are generally earthed through an electrode to avoid shocks when someone touches the body of the equipment. The earth resistance is effected by

a. Depth of electrodes buried in the soil
b. Shape and material of earth electrodes
c. Specific resistance of the soil surrounding the electrode
d. All of these
 Answer  Explanation  Related Ques ANSWER: All of these Explanation: No explanation is available for this question!

30)   The earth resistance can be measured by

a. Fall of potential method
b. Using an earth tester
c. Ducter ohmmeter method
d. Only (a) and (b)
 Answer  Explanation  Related Ques ANSWER: Only (a) and (b) Explanation: No explanation is available for this question!

31)   Earth tester can operates on

a. AC only
b. DC only
c. Both AC and DC
d. None of these
 Answer  Explanation  Related Ques ANSWER: DC only Explanation: No explanation is available for this question!

32)   Megger is used for the measurement of

a. Low resistance
b. Medium resistance
c. High resistance
d. Very high resistance
 Answer  Explanation  Related Ques ANSWER: Very high resistance Explanation: No explanation is available for this question!

33)   AC bridges are used for the measurement of

a. Resistances
b. Resistances and Inductances
c. Inductances and capacitances
d. Resistances, inductances and capacitances
 Answer  Explanation  Related Ques ANSWER: Inductances and capacitances Explanation: No explanation is available for this question!

34)   The commonly used detectors in ac bridges is/are

b. Vibration galvanometers
d. Head phones, tuned amplifiers, vibration galvanometers
 Answer  Explanation  Related Ques ANSWER: Head phones, tuned amplifiers, vibration galvanometers Explanation: No explanation is available for this question!

35)   The vibration galvanometers are sensitive to power for frequency range of

a. 200 Hz and below
b. 200 Hz to about 4 kHz
c. 4 kHz and above
d. Any frequency
 Answer  Explanation  Related Ques ANSWER: 200 Hz and below Explanation: No explanation is available for this question!

36)   The vibration galvanometer used as detector, it responds

a. Only to the fundamental frequency
b. Only to the harmonics frequency
c. Both (a) and (b)
d. Does not respond to any frequency
 Answer  Explanation  Related Ques ANSWER: Only to the fundamental frequency Explanation: No explanation is available for this question!

37)   The Ac Bridge used for the measurement of inductance is/are

a. Maxwell’s inductance bridge
b. Hay’s bridge
c. Anderson’s bridge, Owen’s bridge
d. All of these
 Answer  Explanation  Related Ques ANSWER: All of these Explanation: No explanation is available for this question!

38)   Under balanced condition, the current flowing through the detector is equal to

a. 1 A
b. 0 A
c. Sum of the currents flowing in the adjacent arms
d. Difference between the current flowing in the adjacent arms
 Answer  Explanation  Related Ques ANSWER: 0 A Explanation: No explanation is available for this question!

39)   In Maxwell’s Inductance-Capacitance bridge, the frequency ω

a. Is directly proportional to the inductance in the balanced equation
b. Is inversely proportional to the capacitance in the balanced equation
c. Is directly proportional to the product of inductance and capacitance
d. Does not appear in the balanced equations
 Answer  Explanation  Related Ques ANSWER: Does not appear in the balanced equations Explanation: No explanation is available for this question!

40)   The Maxwell’s Inductance-Capacitance bridge is not suitable for the measurement inductance of coil if the Q factor is

a. Less than 1
b. Between 1 to 10
c. More than 10
d. Both (a) and (c)
 Answer  Explanation  Related Ques ANSWER: Both (a) and (c) Explanation: No explanation is available for this question!