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

1 Answer

Answer :

Material Used for Moving Coil and Former for PMMC Instruments: 

Material used for moving coil: Copper 

Material used for Former: Aluminium

Related questions

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.

Description : Permanent magnet moving coil instruments are used for

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

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 : 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 ... resistance of the battery, in Ohm , is (A) 150 (B) 100 (C) 50 (D) 200

Last 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

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

Last 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

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

Last 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

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

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

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.

Description : Peterson coil is used for :  (A) shunt compensation of lines (B) grounding of system neutral (B) reduce fault currents (D) connecting interconnected systems

Last Answer : Peterson coil is used for : grounding of system neutral

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

Description : State the material used for making (1) Magnetic Core (2) Fuse element  

Last Answer : The material used for making of:  (1) Magnetic Core : Iron, cobalt, Nickel, CRGO, HRGO , silicon steel  (2) Fuse Element: Tin- lead wire, Tinned copper wire 

Description : State properties of conductor material used for overhead conductor. 

Last Answer : Following are the properties of conductor material:-   1. High conductivity :- Material should have high conductivity 2. High mechanical strength:- Material should have sufficiently high mechanical strength ... available & less costly. 9. Scrap Value: - Material should have high scrap value. 

Description : The material used in liquid fuses is  (1) SF6 (3) carbon tetra chloride (2) distilled water (4) transformer oil

Last Answer : The material used in liquid fuses is  carbon tetra chloride

Last Answer : The insulating material used between the commutator segments is normally mica.

Last Answer : The material used for fuse must have low melting point and high specific resistance.

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.

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. 

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  

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

Last 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

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

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.

Description : role of the series resistance connected in PMMC movement.

Last Answer : A PMMC Instrument can be used as voltmeter by just connecting a series resistance with the moving coil. This series resistance is called Voltmeter Multiplier. This combination of moving coil and ... current whose voltage is to be measured. Ideally the resistance of voltmeter should be infinite

Description : feature of PMMC instrument. 

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

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 : State two purposes of calibration of measuring instruments.

Last Answer : Purposes of calibration of measuring instruments: - The purpose of calibration is to ensure that readings of an instrument are consistent with other instruments. It is also important in determining the ... will need to be calibrated periodically to make sure it can function properly and safely. 

Description : State the meaning of secondary instrument. Classify secondary instruments.

Last Answer : Secondary instruments: - Gives reading directly of the quantity being measured. - Calibrated with respect to absolute instruments  Classification of Secondary instruments:  1. Depending on the ... on permissible error: i) Standard meters ii) Substandard meters iii) First grade instruments.

Description : A Peterson coil is ________ A) An arc generating coil B) An arc suppressing coil C) An arc inducing coil D) None of these

Last Answer : A Peterson coil is An arc suppressing coil

Description : lt the length, number of turns and area of a coil are  doubled, the inductance of the coil

Last Answer : lt the length, number of turns and area of a coil are  doubled, the inductance of the coil is quadrupled

Description : The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is_______Vs.

Last Answer : The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is 20 Vs

Description : The rate of rise of current through an inductive coil is maximum?

Last Answer : The rate of rise of current through an inductive coil is maximum at the start of the current flow.

Description : The inductance of a coil can be increased by?

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

Description : Inductance of coil?

Last Answer : Inductance of coil increases with the increase in supply frequency.

Description : Inductance of a coil Varies?

Last Answer : Inductance of a coil Varies as directly as the cross-sectional area of magnetic core and inversely as the length of the iron path.

Description : What is the difference between a coil and an inductor?

Last Answer : Inductor is covering with insulating material is called coil.so they differentiate between coil and inductor.

Description : Compare analog and digital instruments .

Last Answer : Parameter Analog Instrument Digital Instrument  1 Principle The instrument that displays analog signals is called as on analog instrument.  The instrument that displays ... , etc. Logical analyzer, signature analyzer, computers, microprocessor based instruments, etc. 

Description : calibration and the need of calibration for measuring instruments.

Last Answer : Calibration - It is a process of estimating the value of a quantity by comparing that quantity with a standard quantity.    Need of calibration: - Calibration defines the accuracy and ... aim of calibration is to minimize any measurement uncertainty by ensuring the accuracy of test equipment.

Description : Advantages of digital instruments

Last Answer : 1. They are having high input impedance, so there is no loading effect 2. They are having higher accuracy 3. An unambiguous reading is obtained 4. The output can be interfaced with external equipment 5. They are available in smaller size . 

Description : Explain the essential toques in analog type measuring instruments.

Last Answer : List of torques in analog instruments:  1. Deflecting torque  2. Controlling / Restraining torque.  3. Damping torque.  1. Deflecting torque: To create deflection proportional to ... the speed higher will be the damping torque bringing the pointer to the equilibrium position quickly. 

Description : List three types of errors in measuring instruments. Give reasons of occurring for any one of them.

Last Answer : Types of errors in measuring instruments:  A) Gross error: These are due to mistakes on the part of person using the instrument.  B) Systematic Error: i) Instrumental Error: These ... multiplying factor.  C) Random error: These persist even after gross and systematic errors are removed.

Description : Define following terms related to measuring instruments: i) Sensitivity ii) Selectivity.

Last Answer : i) Sensitivity: It is the ratio of the change in output signal to the change in input signal of quantity being measured.  ii) Selectivity: It is the term to describe fulfillment of the requirements of measurement by an instrument to be suitable for use in a given situation. 

Description : List out any four effects of electric current used in measuring instruments & write name of meter working on it.

Last Answer : Effects of Electric Current used in measuring instruments:  1. Magnetic Effect: PMMC and Moving Iron type Ammeters, voltmeter and Dynamometer type wattmeters etc.  2. Electromagnetic induction ... . Electrostatic effect: Voltmeters.  5. Hall Effect: Flux meter, Poynting vector wattmeter.

Description : Describe systematic errors in measuring instruments. 

Last Answer : Systematic errors: -  ➢ Instrumental Error: These errors are caused due to the mechanical structure of measuring instrument.  a) Inherent shortcomings of instruments: Instrument may read ... or electrostatic fields.  ➢ Observational Error: Parallax errors, incorrect multiplying factor. 

Description : Compare primary and secondary instruments.

Last Answer : Primary instruments  Secondary instruments  Gives magnitude of quantity in terms of physical constants of instrument  Gives reading directly of the quantity measured.  Need no calibration  ... .  e.g. magnetic meter, induction meter, hotwire meter and electrostatic meter 

Description : List any four effects employed in measuring instruments.

Last Answer : Effects Employed in Measuring Instruments: 1. Magnetic Effect 2. Electromagnetic induction 3. Heating effect 4. Electrostatic effect 5. Hall Effect 

Description : State the function of overload coil and No volt coil in dc motor starter.

Last Answer : Function of Overload Coil: When DC motor is overloaded, the overload coil carries the overload current and produces strong magnetic field to attract a plunger, which short the terminals of ... dc motor is prevented from restarting automatically on recovery of supply without starter and protected.

Description : State the effect of dead zone on instruments.

Last Answer : It is the largest change in input during which the output remains constant. So during dead zone, even if input changes, output remains the same.

Description : What do you mean by coil?

Last Answer : Ans. Having one or more turns connected in series is called coil.

Description : The purpose of the restraining coil in a biased differential relay is  (A) To reduce CT saturation during fault.  (B) To increase the sensitivity of the relay.  (C) To match the transformation ratio.  (D) To limit the spill current through the relay during heavy external fault.

Last Answer : d

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

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