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A moving-coil permanent-magnet instrument can be used as ammeter by using a low resistance shunt.

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Answer :

A moving-coil permanent-magnet instrument can be used as flux-meter by eliminating the control springs.

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268 views 1 answer
Description :

Name the material used for :- (i) Moving coil (ii) Permanent magnet in PMMC instrument.

Answer :

(i) Material used for Moving coil: Copper, Aluminum( some times)  (ii) Permanent magnets are made of special alloys such as :  Aluminum-Nickel-Cobalt (Alnicos)  Strontium-Iron  Neodymium-Iron-Boron  Samarium-Cobalt.

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136 views 1 answer
Description :

Permanent magnet moving coil instruments are used for

Answer :

PMME are mostly used for measuring voltage and current.

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2.6k views 2 answers
Description :

When the voltage across a battery is measured using a D.C potentiometer, the reading shows 1.08 V. But when the same voltage is measured using a Permanent Magnet Moving Coil (PMMC) voltmeter, the voltmeter reading shows 0.99 V. If the resistance of the voltmeter is 1100 Ohm , the internal resistance of the battery, in Ohm , is (A) 150 (B) 100 (C) 50 (D) 200

Answer :

When the voltage across a battery is measured using a D.C potentiometer, the reading shows 1.08 V. But when the same voltage is measured using a Permanent Magnet Moving Coil (PMMC) voltmeter, ... resistance of the voltmeter is 1100 Ohm , the internal resistance of the battery, in Ohm , is 100

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145 views 1 answer
Description :

Answer :

A moving iron instrument can be used for both D.C. and A.C.

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151 views 1 answer
Description :

Eddy current damping cannot be used for moving iron instrument because

Answer :

Eddy current damping cannot be used for moving iron instrument because the presence of a permanent magnet required for such purpose would affect the deflection and hence the reading of the instrument

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2.2k views 1 answer
Description :

What is permanent magnet and electromagnet?

Answer :

Permanent magnet: A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. As the name suggests, a permanent magnet is 'permanent'. ... an electric current passes through the coil. If the current is interrupted, the magnetism is lost.

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60 views 1 answer
Description :

A neodymium magnet is a permanent magnet made from an alloy of _________ A) Neodymium and iron B) Neodymium, iron and iodine C) Neodymium and boron D) Neodymium, iron and boron

Answer :

A neodymium magnet is a permanent magnet made from an alloy of Neodymium, iron and boron

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59 views 1 answer
Description :

Compare variable reluctance and permanent magnet motors.

Answer :

Variable reluctance Motor  Permanent magnet motors   The rotor is not magnetised The rotor is magnetised  High torque to inertia ratio  Low torque to inertia ratio  ... rotor has salient pole construction The rotor has mostly smooth cylindrical type of construction. 

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2.5k views 1 answer
Description :

A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is (A) 1 Ω (B) 1.001 Ω (C) 0.5 Ω (D) 10 Ω

Answer :

A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is 1.001 Ω

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135 views 1 answer
Description :

A moving coil of meter has 100 turns, and a length and depth of 10mm and 20mm respectively. It is positioned in a uniform radial flux density of 200 mT. The coil carrier current capacity is 50 mA. The torque on the coil is

Answer :

A moving coil of meter has 100 turns, and a length and depth of 10mm and 20mm respectively. It is positioned in a uniform radial flux density of 200 mT. The coil carrier current capacity is 50 mA. The torque on the coil is 200µNm

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338 views 1 answer
Description :

A moving coil meter has a resistance of 3 Ω and gives full scale deflection with 30 mA. To measure voltage up to 300 V, the external resistance to be connected in series with the instrument is (A) 9997 Ω (B) 10000 Ω (C) 997 Ω (D) 10003 Ω

Answer :

A moving coil meter has a resistance of 3 Ω and gives full scale deflection with 30 mA. To measure voltage up to 300 V, the external resistance to be connected in series with the instrument is 9997 Ω

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126 views 1 answer
Description :

State the material used for moving coil and former for PMMC instruments. 

Answer :

Material Used for Moving Coil and Former for PMMC Instruments:  Material used for moving coil: Copper  Material used for Former: Aluminium

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133 views 1 answer
Description :

A permanent magnet moving coil instrument gives full scale deflection of 25mA when a voltage of 75mV is applied across it. Calculate: (i) Resistance of shunt required for full scale deflection of 150 A. (ii) Series resistance for full scale deflection of 500 V.

Answer :

Answer :

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340 views 1 answer
Description :

The self inductance of a coil can be measured using (A) Wien’s Bridge (B) Schering Bridge (C) Anderson’s Bridge (D) Wheatstone Bridge

Answer :

The self inductance of a coil can be measured using Anderson’s Bridge

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61 views 1 answer
Description :

A permanent magnet moving coil ammeter has a coil resistance of 99 ohm and Full Scale Deflection (FSD) current of 0.1mA. Shunt resistance is 1 ohm. Current through the meter at 0.5 F.S.D is:

Answer :

A permanent magnet moving coil ammeter has a coil resistance of 99 ohm and Full Scale Deflection (FSD) current of 0.1mA. Shunt resistance is 1 ohm. Current through the meter at 0.5 F.S.D is: 0.05mA

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217 views 1 answer
Description :

Permanent Magnet Moving Coil (PMMC) Instrument

Answer :

Permanent Magnet Moving Coil (PMMC) Instrument

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Description :

Answer :

In a low power factor wattmeter the compensating coil is connected in series with pressure coil.

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342 views 1 answer
Description :

Answer :

In a low power factor wattmeter the pressure coil is connected to the load side of the current coil.

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178 views 1 answer
Description :

Answer :

The disc of an instrument using eddy current damping should be of conducting and non-magnetic material.

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218 views 1 answer
Description :

An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic field having a component along the axis will be  (1) unaffected (2) decreased (3) increased (4) either decreased or increased depending on the direction of the DC field

Answer :

An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic field having a component along the axis will be either decreased or increased depending on the direction of the DC field

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277 views 1 answer
Description :

Two voltmeters of same range, one moving iron type and other permanent magnet moving coil type, are connected in parallel for measuring a.c. supply voltage. If the reading of MI type is 300V, the reading of PMMC type will be (a) zero (b) higher-than M.I. type (c) lower than M.I. type (d) same

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141 views 0 answers
Description :

Answer :

A moving coil instrument is used as an ohmmeter. The indicating scale of the meter will be Hyperbolic.

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241 views 1 answer
Description :

The inductance of a coil can be increased by?

Answer :

The inductance of a coil can be increased by choosing core material having high relative permeability.

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137 views 1 answer
Description :

Answer :

Meggar is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another.

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260 views 1 answer
Description :

Answer :

A damping device prevents the oscillation of the moving system and enables the latter to reach its final position quickly.

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123 views 1 answer
Description :

Series resistance required to read 0-250 V with a moving coil instrument of internal resistance 2 ohm and full scale deflection of 50 mA is (a) 49998 Ω (b) 4998 Ω (c) 498 Ω (d) 49.8 Ω

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115 views 0 answers
Description :

A moving coil instrument has a resistance of 10 W and gives full scale deflection when carrying a current of 50 mA. To measure current upto 100 A, we will have to connect • 10 W resistance in series • 10 W resistance in parallel • 10/1999 W resistance in series • 10/1999 W resistance in parallel

Answer :

A moving coil instrument has a resistance of 10 W and gives full scale deflection when carrying a current of 50 mA. To measure current upto 100 A, we will have to connect 10/1999 W resistance in parallel

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167 views 1 answer
Description :

Answer :

In a dynamo-meter type of moving coil instrument a swamping resistance is provided inorder to: Provide equal time constant for moving coil and fixed coil, when used for ac measurement

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333 views 1 answer
Description :

 The main sources of Errors in Permanent Magnet moving Coil (PMMC) are due to : - a) weaking of the permanent magnet due to aging at temperature effects b) weaking of spring due to aging and temperature effects c) change of resistance of the moving coil with temperature d) all the above

Answer :

 The main sources of Errors in Permanent Magnet moving Coil (PMMC) are due to : - a) weaking of the permanent magnet due to aging at temperature effects b) weaking of spring due to aging and temperature effects c) change of resistance of the moving coil with temperature d) all the above

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319 views 1 answer
Description :

Answer :

The pointer of an indicating instrument should be very light.

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184 views 1 answer
Description :

Answer :

In a portable instrument, the controlling torque is provided by spring.

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130 views 1 answer
Description :

What is the definition of a primary instrument?

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Description :

Answer :

The multiplier and the meter coil in a voltmeter are in series.

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147 views 1 answer
Description :

The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is (A) 11% (B) 9% (C) 1.1% (D) 3%

Answer :

The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is 11%

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279 views 1 answer
Description :

differences between temporary and permanent magnets

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Description :

Hard steel is suitable for making permanent magnets because?

Answer :

Hard steel is suitable for making permanent magnets because it has good residual magnetism.

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87 views 1 answer
Description :

Those materials are well suited for making permanent magnets which have _____ retentivity and _______ coercivity.

Answer :

Those materials are well suited for making permanent magnets which have high retentivity and high coercivity.

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366 views 1 answer
Description :

Permanent magnets are normally made of?

Answer :

Permanent magnets are normally made of alnico alloys.

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137 views 1 answer
Description :

State the advantages of instrument transformer in using for extension of range of meters. 

Answer :

Advantages of instrument transformer: 1. Extension of instrument range is possible. 2. Isolation of instruments from high voltage side. 3. Power loss is less as compared to shunts and multipliers. 4 ... measurement. 5. It is economical method of range extension. 6. Increases in safety of operator.

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44 views 1 answer
Description :

A Pyrheliometer is an instrument to measure :  (A) temperature of solar photovoltaic cell  (B) intensity of direct solar radiation at normal incidence  (C) intensity of indirect solar radiation  (D) efficiency of a solar photovoltaic cell

Answer :

A Pyrheliometer is an instrument to measure : intensity of direct solar radiation at normal incidence 

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103 views 1 answer
Description :

In a PMMC instrument, the damping provided is :  (A) air damping (C) eddy current damping (B) fluid damping (D) magnetic damping using a magnet

Answer :

In a PMMC instrument, the damping provided is : eddy current damping 

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1.1k views 1 answer
Description :

Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

Answer :

Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

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219 views 1 answer
Description :

Answer :

A multirange instrument has multiple shunt or series resistances inside the meter.

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Description :

Answer :

The scale of a rectifier instrument is linear.

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124 views 1 answer
Description :

Answer :

Instrument transformers are potential transformers, current transformers.

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Description :

Answer :

The rectifier instrument is not free from frequency error.

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167 views 1 answer
Description :

Answer :

The gravity controlled instrument has crowded scale because current is proportional to sine of deflection angle.

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180 views 1 answer
Description :

Answer :

If an instrument has cramped scale for larger values, then it follows logarithmic law.

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93 views 1 answer
Description :

The ratio of maximum displacement deviation to full scale deviation of the instrument is called?

Answer :

The ratio of maximum displacement deviation to full scale deviation of the instrument is called linearity.

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300 views 1 answer
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