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1) An ac voltage source of 2sint V is connected in series with a dc voltage source of 5 V. If a PMMC instrument is connected in parallel to this combination then the reading of meter will be equal to a. 7 V b. 5 V c. 5.2 V d. 25 V
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2) The deflecting torque in a moving coil instrument is a. Directly proportional to the current flowing through it b. Inversely proportional to the current flowing through it c. Inversely proportional to the square of current flowing through it d. Directly proportional to the square of current flowing through it
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3) When an ac signal is applied across the permanent magnet moving coil voltmeter, then the pointer will a. Not deflect b. Oscillate around zero volt c. Deflect to its maximum d. Oscillate from minimum to maximum value
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4) If the control spring of PMMC instrument is replaced by a another spring whose spring constant is higher than the previous one, then the damping ratio and natural frequency a. Increases, decreases b. Increases, increases c. Decreases, decreases d. Decreases, increases
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5) A PMMC instrument can be used as ammeter and as voltmeter with the help of a. A low resistance shunt, a low series resistance b. A low resistance shunt, a high series resistance c. A high series resistance, a low resistance shunt d. A low series resistance, a high shunt resistance
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6) In a PMMC instrument, if the control springs are eliminated the instrument can be used for measuring the quantity of electricity passed through the coil. This method is used for a. Ammeter b. Voltmeter c. Fluxmeter d. Ballistic galvanometer
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7) If the control springs of PMMC instrument is made up of large moment of inertia, then it can be used as a. Ammeter b. Fluxmeter c. Ballistic galvanometer d. Wattmeter
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8) The ratio of maximum current (with shunt) to the full scale deflection current (without current) in a permanent magnet moving coil instrument is known as a. Sensitivity b. Multiplying factor c. Multiplying power d. Both (b) and (c) e. None of these
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9) The multiplying factor of a PMMC used as ammeter is a. Directly proportional to the shunt resistance b. Inversely proportional to the shunt resistance c. Inversely proportional to the series resistance d. Directly proportional to the series resistance
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10) The voltage multiplication factor of a PMMC instrument is a. Directly proportional to the required series resistance b. Directly proportional to the shunt resistance c. Inversely proportional to the shunt resistance d. Directly proportional to the required series resistance
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11) A moving coil ammeter requires a potential difference of 0.4V across it for full scale deflection. It has fixed shunt resistance of 0.01 ohm with a coil circuit resistance of R = 1kohm. The value of shunt required to give full scale deflection when the total current is 10A is equal to a. 0.02 ohm b. 0.04 ohm c. 0.05 ohm d. 0.06 ohm
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12) A PMMC instrument gives full scale deflection at 40 mV potential difference and 8 mA current. What will be the required shunt resistance when it is used as ammeter of range 0 – 10 A? a. 0.002 ohm b. 0.003 ohm c. 0.004 ohm d. 0.005 ohm
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13) A permanent magnet moving coil gives full scale deflection at 40 mV potential difference and 8 mA current. What will be the required series resistance when it is used as voltmeter of range 0 – 200 V? a. 19556 ohm b. 20163 ohm c. 23884 ohm d. 24995 ohm
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14) In electrodynamic instruments, the operating field is produced by a. Permanent magnet b. Fixed coil c. Moving coil d. All of these
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15) Electrodynamic instruments can be used as a. Ammeter b. Voltmeter c. Wattmeter d. All of these
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16) The scale of electrodynamic instrument when it is used as ammeter and when it is used as voltmeter is a. Uniform, uniform b. Crowded near zero, crowded near zero c. Cramped near zero, cramped in the middle d. Uniform, cramped near zero
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17) In an electrodynamic instrument, the number of control springs present is / are a. Two b. One c. Four d. Zero
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18) The deflection angle in hot wire instruments is a. Directly proportional to the current b. Directly proportional to the square of current c. Inversely proportional to the current d. Inversely proportional to the square of current
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19) Hot-wire instruments are suitable for a. AC work only b. DC work only c. Both AC and DC work d. None of these
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20) The current sensitive instruments are a. PMMC b. Hot wire instruments c. Electrostatic instruments d. Both (a) and (b)
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