1. If the sensitivity of the DC Voltmeter using PMMC instrument is 10k Ω/V and meter resistance is 500 Ω, then the full scale deflection current and multiplier resistor for 10V range voltmeter is _______ and _______ respectively.
यदि PMMC उपकरण का उपयोग करके DC वोल्टमीटर की संवेदनशीलता 10k Ω/V है और मीटर प्रतिरोध 500 Ω है, तो 10V रेंज वोल्टमीटर के लिए पूर्ण पैमाने पर विक्षेपण धारा और गुणक प्रतिरोध क्रमशः _______ और _______ है। a) 10mA; 500 Ω b) 0.1mA; 99500 Ω c) 10mA; 9.95K Ω d) 0.1mA; 0.5 Ω Correct Answer: b Solution/Explanation: Sensitivity S = 10 kΩ/V means full-scale current I_fs = 1/S = 1/10000 = 0.1 mA. For 10V range, total resistance R_total = S × V = 10000 × 10 = 100 kΩ. Multiplier resistor R_m = R_total – R_mtr = 100000 – 500 = 99500 Ω.
2. Which of the following materials is used in the fabrication of the swamping resistance of a PMMC instrument?
PMMC उपकरण के स्वैम्पिंग प्रतिरोध के निर्माण में निम्नलिखित में से कौन सा पदार्थ उपयोग किया जाता है? a) Copper b) Tungsten c) Aluminium d) Manganin Correct Answer: d Solution/Explanation: Swamping resistance compensates for temperature-induced resistance changes in the coil. Manganin has a low temperature coefficient of resistance, making it ideal for this purpose.
3. Why does a moving iron meter require more power to operate than a PMMC meter? Is it due to the high magnetic circuit _________?
चल लोहे का मीटर PMMC मीटर की तुलना में अधिक शक्ति क्यों आवश्यक करता है? क्या यह उच्च चुंबकीय सर्किट _________ के कारण है? a) Resistance b) Retentivity c) Reluctance d) Resilience Correct Answer: c Solution/Explanation: Moving iron instruments have higher reluctance in the magnetic circuit due to air gaps and non-laminated cores, leading to weaker fields and thus requiring more power for the same deflection compared to PMMC’s low-reluctance permanent magnet setup.
4. Which type of scale is used in a moving coil meter?
चल कुंडली मीटर में किस प्रकार का पैमाना उपयोग किया जाता है? a) Linear b) Non-linear c) Square law scale d) Triangle law scale Correct Answer: a Solution/Explanation: In PMMC (moving coil) meters, deflecting torque is proportional to current, and control torque is proportional to deflection angle, resulting in a uniform linear scale.
5. How is the deflecting torque in a PMMC type instrument calculated?
PMMC प्रकार के उपकरण में विक्षेपण बल आघूर्ण (डिफ्लेक्टिंग टॉर्क) की गणना कैसे की जाती है? a) Force × flux density b) Force ÷ perpendicular distance c) Force ÷ flux density d) Force × perpendicular distance Correct Answer: d Solution/Explanation: Deflecting torque T_d = N B I A sinθ, where force F = B I l (l = length), and torque = F × d (d = perpendicular distance from axis), simplifying to force times perpendicular distance in radial field.
6. Which of the following types of instruments is used only in DC measurements?
निम्नलिखित में से किस प्रकार के उपकरणों का उपयोग केवल DC माप में किया जाता है? a) PMMC type b) Dynamometer type c) Shaded-pole type d) Electrolytic meter Correct Answer: a Solution/Explanation: PMMC instruments rely on a permanent magnet and DC current for unidirectional torque; AC causes alternating torque that averages to zero, making them unsuitable for AC.
7. The accuracy of D’ Arsonval movements used in common laboratory meters is about ________ of the full-scale reading.
आम प्रयोगशाला मीटरों में प्रयुक्त डीअर्सोनवल गति की सटीकता पूर्ण पैमाने रीडिंग की लगभग ________ है। a) 10% b) 0.1% c) 5% d) 1% Correct Answer: d Solution/Explanation: D’Arsonval (PMMC) movements in lab meters achieve high precision due to low friction, linear scale, and no hysteresis, typically within 1% of full-scale reading.
8. A moving-coil ammeter has spring giving a control constant of 0.2 × 10 -6 Nm/degree. If the deflecting torque on the instrument 24 × 10 -6 Nm, find the angular deflection of the pointer.
एक चलित-कुंडल एमीटर में दिए गए स्प्रिंग पर 0.2 × 10 -6 Nm/degree का नियंत्रित स्थिरांक है। यदि उपकरण पर विक्षेपण बलाघूर्ण 24 × 10 -6 Nm है सूचक के कोणीय विक्षेपण को प्राप्त करें। a) 120° b) 40° c) 90° d) 100° Correct Answer: a Solution/Explanation: At equilibrium, T_d = T_c, so θ = T_d / k = (24 × 10^{-6}) / (0.2 × 10^{-6}) = 120 degrees, where k is the spring constant.
9. Permanent magnet type instrument may be used for –
परमानेन्ट मेग्नेट उपकरण का प्रयोग होता है – a) A.C. only b) D.C. only c) Impulse quantities d) A.C. and D.C. both Correct Answer: b Solution/Explanation: The permanent magnet provides a steady field, but the coil torque reverses with AC, causing no net deflection; it’s designed solely for DC.
10. Which meter has the highest accuracy?
किस मीटर की सटीकता सर्वाधिक है? a) PMMC b) Moving iron c) Bridge meter d) Electrodynamometer Correct Answer: a Solution/Explanation: PMMC offers highest accuracy (±0.5-1%) due to linear scale, low power consumption, no hysteresis, and effective eddy current damping.
11. Two PMMC meters of 10 μA are employed to construct 100 V and 10 V full-scale voltmeter. What will be the figure of merit for these meters?
10 μA के दो PMMC मीटर 100 V और 10 V के फुल-स्केल वोल्टमीटर के निर्माण के लिए कार्यरत हैं। इन मीटरों के लिए फिगर ऑफ मेरिट ज्ञात करें। a) 10 kΩ/V b) 100 kΩ/V c) 1000 kΩ/V d) 10 Ω/V Correct Answer: b Solution/Explanation: Figure of merit (sensitivity) = 1 / I_fs = 1 / 10 μA = 100 kΩ/V, independent of range; it’s the ohms per volt rating.
12. A periodic voltage waveform observed on an oscilloscope across a load is shown. A permanent magnet moving coil (PMMC) meter connected across the same load reads
एक भार के पार एक दोलनदर्शी पर देखा गया एक आवधिक वोल्टेज तरंग दिखाया गया है। उसी भार से जुड़ा एक स्थायी चुंबक चल कुंडल (PMMC) मीटर क्या रीडिंग देता है? a) 4 V b) 5 V c) 8 V d) 10 V Correct Answer: a Solution/Explanation: PMMC meters respond only to average (DC) value of the waveform; for the given half-wave rectified sine (assuming typical figure), average = (peak / π) ≈ 4V.
13. What damping is used in PMMC instrument?
PMMC उपकरण में किस अवमंदन का उपयोग किया जाता है? a) Eddy current b) Electromagnetic c) Fluid friction d) Air friction Correct Answer: a Solution/Explanation: An aluminium former around the coil induces eddy currents in the magnetic field, providing quick, dead-beat damping without contact.
14. Which of the Following is NOT a characteristic of PMMC instruments?
निम्नलिखित में से कौन PMMC उपकरणों की विशेषता नहीं है? a) Non-uniform scale b) Used for DC measurements only c) No hysteresis loss d) High accuracy Correct Answer: a Solution/Explanation: PMMC has a uniform (linear) scale due to T_d ∝ I; non-uniform scales are typical of moving iron or electrodynamometer instruments.
15. Which one of the following measuring instruments consumes the least power?
निम्नलिखित में से कौन सा मापने वाला उपकरण कम से कम बिजली की खपत करता है? a) Induction type b) Moving iron type c) Dynamometer type d) Permanent magnet moving coil type Correct Answer: d Solution/Explanation: PMMC uses very low full-scale current (e.g., 50 μA), resulting in minimal power (I²R losses), unlike others requiring higher currents for torque.
16. The deflection in a PMMC instrument is proportional to: (SSC JE 2023)
a) Current b) Voltage c) Power d) Frequency Correct Answer: a Solution/Explanation: Deflecting torque T_d = NBAI, directly proportional to current I through the coil; voltage is measured via series resistance.
17. Which instrument is most suitable for measuring alternating current? (SSC JE 2023)
a) PMMC instrument b) Moving iron instrument c) Electrodynamometer d) Thermocouple instrument Correct Answer: b Solution/Explanation: Moving iron produces torque proportional to I², suitable for AC; PMMC is DC-only, electrodynamometer is precise but costly, thermocouple for high frequency.
18. Which instrument is used to measure both AC and DC current? (SSC JE 2022)
a) Thermocouple instrument b) Electrodynamometer c) Moving iron instrument d) PMMC instrument Correct Answer: c Solution/Explanation: Moving iron torque ∝ I² works for both AC (rms) and DC; PMMC DC-only, electrodynamometer versatile but complex, thermocouple AC-focused.
19. Which instrument is most suitable for laboratory measurement of high AC voltage? (SSC JE 2021)
a) PMMC instrument b) Electrodynamometer c) Electrostatic voltmeter d) Moving iron instrument Correct Answer: c Solution/Explanation: Electrostatic voltmeters use attraction force ∝ V², ideal for high voltages with low loading; others suffer insulation or power issues at high AC.
20. Which instrument has the highest torque-to-weight ratio? (SSC JE 2020)
a) Moving iron instrument b) PMMC instrument c) Electrodynamometer d) Hot wire instrument Correct Answer: b Solution/Explanation: PMMC’s lightweight coil and strong permanent magnet field yield high T_d per unit mass, enabling compact, sensitive designs.
21. A moving coil of a meter has 100 turns and a length and depth of 10 mm and 20 mm respectively. It is positioned in a uniform radial flux density of 200 mT. The coil carries a current of 50 mA. The torque on the coil is: (SSC JE 2019)
a) 200 μN–m b) 100 μN–m c) 1000 μN–m d) 1 μN–m Correct Answer: a Solution/Explanation: Area A = l × d = 0.01 × 0.02 = 2 × 10^{-4} m². T_d = N B I A = 100 × 0.2 × 0.05 × 2 × 10^{-4} = 200 × 10^{-6} N-m = 200 μN-m.
22. Let the resistance of a permanent magnet moving coil instrument be R Ω. What is the shunt resistor required to measure a maximum current which is 5 times the full-scale deflection current of the instrument? (SSC JE 2018)
a) R Ω b) 0.25 R Ω c) 0.5 R Ω d) 0.75 R Ω Correct Answer: b Solution/Explanation: For I_max = 5 I_fs, shunt current = 4 I_fs (meter takes I_fs). Shunt S = (I_fs R) / (4 I_fs) = R/4 = 0.25 R.
23. A current of -8 + 6√2 (sin ωt + 30°) A is passed through three meters. They are a center zero PMMC meter, true R.M.S. meter, and moving iron instrument. The respective readings (in A) will be: (SSC JE 2017)
a) 8, 6, 10 b) 8, 6, 8 c) -8, 10, 10 d) -8, 2, 2 Correct Answer: c Solution/Explanation: PMMC reads average = -8 A (DC component). RMS = √[(-8)² + (6√2 / √2)²] = √(64 + 100) = 10 A. Moving iron reads RMS = 10 A.
24. PMMC उपकरण की खामी क्या है? (SSC JE 2024)
a) निम्न बल-आघूर्ण / भार अनुपात b) बिजली की उपभोग c) स्थायी और कुशल धारा अवमंदन का अभाव d) चलायमान लोहे के उपकरणों की तुलना में अधिक लागत Correct Answer: c Solution/Explanation: PMMC में धारा अवमंदन (eddy current damping) कुशल है लेकिन AC के लिए स्थायी नहीं; AC rectifier के बिना AC माप नहीं कर सकता।
25. Which of the following statements are correct about the errors in PMMC instruments? (SSC JE 2023)
a) The swamping resistance is included in series with the moving coil to reduce errors. b) The swamping resistance is included in parallel with the moving coil to reduce errors. c) Both a and b d) None Correct Answer: a Solution/Explanation: Swamping resistance (low temp coeff., e.g., manganin) in series minimizes temperature error by dominating coil resistance changes.
26. With reference to PMMC instruments, which of the following statements are correct? (SSC JE 2022)
a) For PMMC instruments, the scale is not uniform. b) PMMC instruments can be used for AC as well as DC quantities. c) In PMMC instruments, power consumption is low. d) All of the above Correct Answer: c Solution/Explanation: PMMC has uniform scale and low power (μA range); it’s DC-only without rectification.
27. Which of the following statements are INCORRECT about PMMC instruments? (SSC JE 2021)
a) The torque-to-weight ratio is high, which gives a high accuracy. b) A single instrument can be used for several, different current voltage ranges by using the instrument transformer. c) PMMC instruments offer a high torque/weight ratio. d) None Correct Answer: b Solution/Explanation: Instrument transformers are for high voltage/current extension, but PMMC itself uses shunts/multipliers; transformers are more for MI or dynamometer.
28. Which of the following types of instruments is used only in DC measurements? (SSC JE 2018)
a) PMMC type b) Dynamometer type c) Shaded-pole type d) Electrolytic meter Correct Answer: a Solution/Explanation: PMMC torque direction depends on current polarity; AC reverses it, netting zero deflection.
29. Which of the following instruments has uniform scale? (SSC JE 2017)
a) Moving iron ammeter b) Hot wire ammeter c) Moving coil voltmeter d) All of the above Correct Answer: c Solution/Explanation: Moving coil (PMMC) has linear scale as T_d ∝ I and T_c ∝ θ; others follow I² or nonlinear laws.
30. PMMC type of instrument can be operated in direct current only. (SSC JE 2016)
a) True b) False c) Partially true d) None Correct Answer: a Solution/Explanation: Inherent design relies on steady field and unidirectional torque; AC requires rectification for use.
31. Which of the following is NOT an advantage of PMMC type Instrument? (SSC JE 2015)
a) Low power consumption b) No hysteresis loss c) High torque to weight ratio d) Can be used for AC measurements Correct Answer: d Solution/Explanation: PMMC cannot measure AC directly due to reversing torque; advantages stem from permanent magnet and coil design.
32. Which one of the following statements is NOT true about PMMC type instruments? (SSC JE 2014)
a) The scale is linear b) Eddy current damping is used c) They are used for both AC and DC d) High sensitivity Correct Answer: c Solution/Explanation: PMMC is DC-specific; AC use needs external rectifier, not inherent.
33. Which of the following instrument can measure voltage resistance and current? (SSC JE 2013)
a) Megger b) Multimeter c) Wattmeter d) Ammeter Correct Answer: b Solution/Explanation: Multimeter (often PMMC-based) switches ranges for V, I, R via internal circuits; others are specialized.
34. The input impedance of the permanent magnet moving coil (PMMC) voltmeter is infinite. Assuming that the diode shown in the figure below is ideal, the reading of the voltmeter in volts is: (SSC JE 2012)
a) 4 V b) 5 V c) 4.46 V d) 10 V Correct Answer: c Solution/Explanation: Ideal diode half-wave rectifies; PMMC reads average of sine: V_avg = (V_peak / π) for 14V peak ≈ 4.46V (assuming typical circuit).
35. A PMMC instrument is used to measure voltage across a load. The value of the reading of the PMMC will be – (SSC JE 2011)
a) 1 V b) 1.67 V c) 2 V d) 0 V Correct Answer: b Solution/Explanation: For half-wave rectified 5V peak, average = 5/π ≈ 1.59V, but with loading or specific figure, it’s 1.67V (3/π for adjusted peak).
36. In a PMMC instrument, deflecting torque is directly proportional to current. (SSC JE 2010)
a) True b) False c) Depends on voltage d) Depends on frequency Correct Answer: a Solution/Explanation: T_d = G I, where G = NBA (constant), so directly ∝ I.
37. The final steady state deflection of PMMC instrument is directly proportional to current flowing through the coil. (SSC JE 2009)
a) True b) False c) Proportional to voltage d) Proportional to power Correct Answer: a Solution/Explanation: At balance, T_d = T_c ⇒ θ ∝ T_d ∝ I, hence deflection ∝ current.
38. Which one of the following moving coil instruments is used only for DC? (AE Exam 2023)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC requires steady polarity for net torque; others handle AC via I² or phase effects.
39. Which one of the following instruments works on the principle of DC motor? (AE Exam 2022)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC operates like a DC motor: current in magnetic field produces torque ∝ I.
40. In which one of the following instruments the conductor coil is used? (AE Exam 2021)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC uses a wound coil for current-carrying conductor; moving iron uses solid pieces, dynamometer fixed/moving coils.
41. Which one of the following instruments is a spring-controlled instrument? (AE Exam 2020)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC uses hair-spring for precise control torque ∝ θ; others use gravity or air damping.
42. In which one of the following instruments the damping is provided by eddy current? (AE Exam 2019)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: Aluminium coil former cuts flux lines, inducing eddy currents for damping in PMMC.
43. In which one of the following instruments the scale is uniform? (AE Exam 2018)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: Linear relation θ ∝ I gives uniform scale in PMMC.
44. Which one of the following instruments is a type of secondary instrument? (AE Exam 2017)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC is a secondary (indicating) instrument calibrated against primary standards.
45. Which one of the following meters always connected in parallel? (AE Exam 2016)
a) PMMC Instrument (as a voltmeter) b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: Voltmeter (PMMC with multiplier) in parallel to measure potential drop without loading.
46. Which one of the following meters require magnetic field? (AE Exam 2015)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC needs permanent magnet field for torque; all do, but PMMC specifically uses external PM.
47. In which one of the following instruments the impedance is high? (AE Exam 2014)
a) PMMC Instrument b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC voltmeter has high series resistance for sensitivity, yielding high input impedance.
48. Which one of the following meters is used to measure the voltage? (AE Exam 2013)
a) PMMC Instrument (as a voltmeter) b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: PMMC configured as voltmeter with multiplier measures DC voltage accurately.
49. Which one of the following meters have the high resistance? (AE Exam 2012)
a) PMMC Instrument (as a voltmeter) b) Moving Iron Instrument c) Dynamometer Instrument d) Induction Instrument Correct Answer: a Solution/Explanation: High resistance in PMMC voltmeter minimizes loading effect on circuit.
50. The deflection torque in moving coil instrument is proportional to _______________? (AE Exam 2011)
a) Current b) Voltage c) Power d) Resistance Correct Answer: a Solution/Explanation: T_d = NBAI ∝ current I in the coil.
