1 Answer

Answer :

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

Related questions

Last Answer : In a moving iron meter, the deflecting torque is proportional to Square of the current through the coil.

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

Last Answer :  In a ballistic galvanometer, the deflecting torque is proportional to the current through coil.

Description : Which of the following instruments have least torque/weight ratio: a) Dynamometer type b) PMMC c) Attraction type moving iron d) Repulsion type moving iron

Last Answer : Ans: A

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

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

Description : When both deflecting and controlling torque act, the pointer of an indicating instrument comes to

Last Answer : rest

Description : If the pointer of an indicating instrument is in motion, then what opposes deflecting torque?

Last Answer : damping and controlling torque

Description : The torque produced in wattmeter is proportional to

Last Answer : A

Description : Draw the construction and explain working principle of PMMC instruments

Last Answer : Working: When current passes through the coil a deflecting torque is produced. This deflecting torque is produced due to interaction between magnetic field produced by permanent magnet ... equilibrium; this is possible only when the controlling torque becomes equal to the deflecting torque 

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

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

Description : Controlling torque in PMMC

Last Answer : spring action

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.

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

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 

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

Description : PMMC instrument gives uniform scale because:

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

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

Last Answer : The rectifier instrument is not free from frequency error.

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

Description : The type of instruments used mainly for standardizing instruments in laboratories is (a) Indicating instrument (b) Integrating instrument (c) Absolute instrument (d) Recording instrument  

Last Answer : Ans:Option C

Description : Electrostatic type instruments are primarily used as 

Last Answer : Voltmeter

Description : In laser printers, printing is achieved by deflecting laser beam on to __________ surface of a drum. A. Magnetic B. Electric C. Photosensitive D. None of the Above

Last Answer : C. Photosensitive

Description : Minimum radius of a simple circular curve deflecting through 5°, is (A) 1618.9 m (B) 1816.9 m (C) 1718.9 m (D) 1817.9 m

Last Answer : Answer: Option C

Description : Which of the following instruments can be used for measurement of very high value resistances such as insulation resistance in industries? A) Wheatstone bridge B) Megger C) Ohm-meter D) Resistive potentiometer 

Last Answer : Which of the following instruments can be used for measurement of very high value resistances such as insulation resistance in industries? A) Wheatstone bridge B) Megger C) Ohm-meter D) Resistive potentiometer 

Description :  Highest flux density exists inside which of the following instruments? A) Electrodynamic instruments B) Hot wire instruments C) Moving iron instruments D) Moving coil instruments

Last Answer : Highest flux density exists inside which of the following instruments? A) Electrodynamic instruments B) Hot wire instruments C) Moving iron instruments D) Moving coil instruments 

Description : Eddy current damping is normally used in the instruments of (a) Induction type (b) Moving iron type (c) Permanent magnet moving coil type (d) Nothing can be said 

Last Answer : Permanent  magnetic  moving  coil  instrument.

Description : The force required to move the pointer in an indicating instruments is

Last Answer : The force required to move the pointer in an indicating instruments is deflecting force

Description : Horizontally mounted moving iron instruments use   (a) Eddy current damping (b) Electromagnetic damping (c) Fluid friction damping (d) Air friction damping

Last Answer : Horizontally mounted moving iron instruments use Air friction damping

Description : Permanent magnet moving coil instruments are used for

Last Answer : PMME are mostly used for measuring voltage and current.

Last Answer : Thermocouple instruments are also known as Rectifier instruments.

Last Answer :  Electrostatic instruments are normally used for High voltage measurements.

Description : Which of the following instruments can be used to measure AC current only? (a) Permanent Magnet Type ammeter(b) Induction type ammeter (c) Moving iron voltmeter(d) Moving iron ammeter

Last Answer : (b) Induction type ammeter

Last Answer : Jewels are used in instruments for the purpose of Bearing.

Last Answer : The thermocouple instruments do not have High degree of measuring accuracy.

Last Answer : The electrostatic instruments can be used without serious loss of accuracy upto 100kHz frequency.

Last Answer : Integrating instruments are those which measure the total quantity of electricity delivered in a particular time.

Description : The use of _____ instruments is merely confined within laboratories as standardising instruments.

Last Answer : The use of absolute instruments is merely confined within laboratories as standardizing instruments.

Last Answer : Air friction damping is used in the instruments which is: Moving iron

Last Answer : Commonly used instruments in power system measurement are induction.

Last Answer : Operating torques in analogue instruments are deflecting, control and damping.

Last Answer : The power factor of a single phase load can be calculated if the instruments available are three ammeters or three voltmeters.

Last Answer : The switch board instruments should be mounted in vertical position.

Last Answer : In the majority of instruments, damping is provided by eddy currents.

Last Answer : According to application, instruments are classified as switch board, portable.

Last Answer : Integrating instruments are those which measure the total quantity of electricity delivered in a particular time.

Last Answer : The use of absolute instruments is merely confined within laboratories as standardizing instruments.

Description : What do you mean by secondary instruments?

Last Answer : The instruments which will give the direct readings are called secondary instruments

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 

Description : Ideally, the damping torque should be  (1) Proportional to velocity of the moving system and operating current.  (2) Proportional to the velocity of the moving system but independent of operating ... operating current.  (4) Independent of the velocity of the moving system and operating current.

Last Answer : Ideally, the damping torque should be Proportional to the velocity of the moving system but independent of operating current.