PMMC instrument gives uniform scale because:

PMMC instrument gives uniform scale because:
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Answer :

PMMC instrument gives uniform scale because: It uses spring control and The deflection torque is proportional to the instrument current.
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Related questions

In a PMMC instrument, the damping provided is :

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

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

A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an

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

Last 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

A PMMC instrument can be used as a fluxmeter by:

Last Answer : A PMMC instrument can be used as a fluxmeter by: Removing the control spring

A moving coil instrument has a resistance of 10 W and gives full scale deflection when carrying

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

Last 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

The gravity controlled instrument has crowded scale because current is proportional to?

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

PMMC type instruments normally use

Last Answer : PMMC type instruments normally use Eddy current damping.

In the case of PMMC rectifier type instruments, the deflecting torque is proportional to

Last Answer : In the case of PMMC rectifier type instruments, the deflecting torque is proportional to Average value of AC current.

Moving iron and PMMC instruments can be distinguished from each other by looking at:

Last Answer : Moving iron and PMMC instruments can be distinguished from each other by looking at: Scale

Basically, a PMMC instrument can be used only in

Description : Basically, a PMMC instrument can be used only in

Last Answer : dc measurements

Another name for PMMC instrument

Description : Another name for PMMC instrument

Last Answer : D'Arsonval

Derive the relation for deflection torque in PMMC instrument.

Description : Derive the relation for deflection torque in PMMC instrument. 

Last Answer : Ans: The length of coil be l meter and width of coil be d meter. Assume I is the current flowing in the ciol having N turns. Assume B as the flux density in the air gap then F=BIL ... a direct indication of the current in the coil. The pointer deflection can therefore be used to measure current.

Draw the diagram of PMMC instrument and state the deflection torque equation

Description : Draw the diagram of PMMC instrument and state the deflection torque equation

Last Answer : Equation Ʈ= B*A*I*N Where r= torque Newton. Meter B = flux density in the air gap. Wb/m2 A = effective coil area (m) N= number of turns of wire of the coil

List two advantages of PMMC instrument.

Description : List two advantages of PMMC instrument.

Last Answer : 1. It has uniform scale. 2. Power consumption is low 3. It can be obtained in wide ranges. 4. High sensitivity & accuracy 5. It is unaffected by external magnetic field. 6. Additional damping device not required. 7. Hysteresis problem is not there.

Permanent Magnet Moving Coil (PMMC) Instrument

Description : Permanent Magnet Moving Coil (PMMC) Instrument

Last Answer : Permanent Magnet Moving Coil (PMMC) Instrument

State the working principle of PMMC Analog instrument.

Description : State the working principle of PMMC Analog instrument.

Last Answer : Working Principal of PMMC Analog Instrument: When current carrying conductor is placed in a magnetic field, it experiences mechanical force. In PMMC instrument, when current flows through a coil ... coil rotates and pointer attached to the coil shows deflection proportional to the current magnitude.

feature of PMMC instrument.

Description : feature of PMMC instrument. 

Last Answer : Consumes less power Great accuracy. High torque to weight ratio

State the function of former and control spring in PMMC instrument.

Description : State the function of former and control spring in PMMC instrument.

Last Answer : Function of Former: To support the coil and provide eddy current damping.  Function of Control Spring: To provide control torque or force and in some instruments springs can be used as current leads.

‘PMMC instrument is not suitable to measure AC quantity’. State the reason.

Description : ‘PMMC instrument is not suitable to measure AC quantity’. State the reason.

Last Answer : The direction of force exerted on moving coil depends on the direction of current flowing through moving coil. If the direction of magnetic field is kept constant, it produces unidirectional torque if the current is ... on the coil in one cycle to zero. Hence the meter cannot read A.C. quantities.

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

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

Last 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.

State working principle of PMMC instrument.

Description : State working principle of PMMC instrument.

Last Answer : Working Principle of PMMC Instrument: When current carrying conductor is placed in a constant magnetic field, it experiences a force proportional to the current and produces proportional deflection torque. 

Compare PMMC & MI instrument.

Description : Compare PMMC & MI instrument.

Last Answer : MI Instrument  PMMC Instrument  It works on the principles of magnetism.  It works on the principle of DC motor Deflection torque is proportional to square of current  Deflection ... , Voltmeter and Watt meter  Can be used as voltmeter, Ammeter, Galvanometer, ohmmeter  

Which of the following factors limit the deflection of the pointer of a PMMC instrument of about

Description : Which of the following factors limit the deflection of the pointer of a PMMC instrument of about 90o?  1. Its damping mechanism  2. Linearity of magnetic field in which the coil moves  3. Control spring arrangement  4. ... Only 1 and 3 (b) Only 2 and 4 (c) Only 2 and 3 (d) Only 1 and 4 

Last Answer : Which of the following factors limit the deflection of the pointer of a PMMC instrument of about 90o?  1. Its damping mechanism  2. Linearity of magnetic field in which the coil moves  3. Control spring arrangement  4. ... Only 1 and 3 (b) Only 2 and 4 (c) Only 2 and 3 (d) Only 1 and 4 

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

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

If an instrument has cramped scale for larger values, then it follows?

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

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

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

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

The scale of a rectifier instrument is?

Last Answer : The scale of a rectifier instrument is linear.

What is the reason why the scale of a permanent-magnet moving coil instrument is uniform?

Description : What is the reason why the scale of a permanent-magnet moving coil instrument is uniform?

Last Answer : because it is spring controlled

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.

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.

Last Answer : Answer :

Eddy current damping cannot be used for moving iron instrument because

Description : Eddy current damping cannot be used for moving iron instrument because

Last 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

Flywheel is an important part of a steam engine because it – (1) accelerates the speed of the engine (2) helps the engine in keeping the speed uniform (3) decreases the moment of inertia (4) gives strength to the engine

Description : Flywheel is an important part of a steam engine because it – (1) accelerates the speed of the engine (2) helps the engine in keeping the speed uniform (3) decreases the moment of inertia (4) gives strength to the engine

Last Answer : (2) helps the engine in keeping the speed uniform Explanation: A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a. significant moment of ... the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.

Flywheel is an important part of a steam engine because it - (1) gives strength to the engine (2) accelerates the speed of the engine (3) helps the engine in keeping the speed uniform (4) decreases the moment of Inertia

Description : Flywheel is an important part of a steam engine because it - (1) gives strength to the engine (2) accelerates the speed of the engine (3) helps the engine in keeping the speed uniform (4) decreases the moment of Inertia

Last Answer : (3) helps the engine in keeping the speed uniform

Flywheel is an important part of a steam engine because it – (1) accelerates the speed of the engine (2) helps the engine in keeping the speed uniform (3) decreases the moment of inertia (4) gives strength to the engine

Description : Flywheel is an important part of a steam engine because it – (1) accelerates the speed of the engine (2) helps the engine in keeping the speed uniform (3) decreases the moment of inertia (4) gives strength to the engine

Last Answer : (2) helps the engine in keeping the speed uniform Explanation: A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a. significant moment of ... the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.

Flywheel is an important part of a steam engine because it - (1) gives strength to the engine (2) accelerates the speed of the engine (3) helps the engine in keeping the speed uniform (4) decreases the moment of Inertia

Description : Flywheel is an important part of a steam engine because it - (1) gives strength to the engine (2) accelerates the speed of the engine (3) helps the engine in keeping the speed uniform (4) decreases the moment of Inertia

Last Answer : (3) helps the engine in keeping the speed uniform

Flywheel is an important part of a steam engine because it : (1) accelerates the speed of the engine (2) helps the engine in keeping the speed uniform (3) decreases the moment of inertia (4) gives strength to the engine

Description : Flywheel is an important part of a steam engine because it : (1) accelerates the speed of the engine (2) helps the engine in keeping the speed uniform (3) decreases the moment of inertia (4) gives strength to the engine

Last Answer : helps the engine in keeping the speed uniform

The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the

Description : The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are  A) Perpendicular B) Parallel C) Inclined at 60" D) Inclined at 30°

Last Answer : The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are Parallel 

In the case of an instrument reading of 8.3 V with a 0 to 150 voltmeter having a guaranteed accuracy of

Description :  In the case of an instrument reading of 8.3 V with a 0 to 150 voltmeter having a guaranteed accuracy of 1% full scale reading, the percentage limiting error is   (A) 1.810% (B) 0.181% (C)12.45% (D) 0.0018%

Last Answer :  In the case of an instrument reading of 8.3 V with a 0 to 150 voltmeter having a guaranteed accuracy of 1% full scale reading, the percentage limiting error is 12.45%

A Pyrheliometer is an instrument to measure :

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

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

Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type

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

Last 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

Electrostatic instrument uses the principle of the variation of

Last Answer : Electrostatic instrument uses the principle of the variation of Capacitance with the voltage.

In a gravity controlled instrument, the deflection angle is proportional to

Last Answer :  In a gravity controlled instrument, the deflection angle is proportional to sine inverse of measurand.

In a moving coil instrument, the deflecting torque is proportional to

Last Answer :  In a moving coil instrument, the deflecting torque is proportional to Current.

The repeat accuracy of an instrument can be judged from its

Last Answer : The repeat accuracy of an instrument can be judged from its standard deviation of error.

If the instrument is to have a wide range, the instrument should have

Last Answer : If the instrument is to have a wide range, the instrument should have Logarithmic scale.

The error of an instrument is normally given as a percentage of

Last Answer : The error of an instrument is normally given as a percentage of full-scale value.

An instrument to be used for measurement and control should preferably have

Last Answer : An instrument to be used for measurement and control should preferably have Linear output and fast response

For the indicating instrument the preferred damping condition is

Last Answer : For the indicating instrument the preferred damping condition is  a damping coefficient of 0.8 to 1.

The sensitivity of an instrument is

Last Answer : The sensitivity of an instrument is ratio of the change in the magnitude of the output to the corresponding change in the magnitude of the input.

The percentage limiting error, in the case of an instrument reading ...

Description :  The percentage limiting error, in the case of an instrument reading of 8.3V with a 0 to 150V voltmeter having a guaranteed accuracy of 1% full-scale reading is

Last Answer :  The percentage limiting error, in the case of an instrument reading of 8.3V with a 0 to 150V voltmeter having a guaranteed accuracy of 1% full-scale reading is 18.10%.

An instrument transformer is used to extend the range of

Last Answer : An instrument transformer is used to extend the range of induction instrument.

The instrument having its deflection depends upon average value is:

Last Answer : The instrument having its deflection depends upon average value is:  Rectifier type