PMMC Instrument kya hai And Working Principle of PMMC Instrument.

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PMMC Instruments

Definition:
PMMC (Permanent Magnet Moving Coil) instruments ek electromechanical devices hote hain jo electrical current ya voltage measure karte hain. Ye instruments high accuracy, sensitivity aur linear scale ke liye jaane jaate hain. Inka construction ek moving coil hota hai jo ek permanent magnet ke magnetic field mein placed hota hai.


Working Principle

PMMC instruments ka working principle permanent magnet ke magnetic field aur ek current-carrying coil ke magnetic field ke interaction par based hota hai. Yahan ek step-by-step explanation hai:

1. Construction:

Permanent Magnet: Ye ek constant magnetic field provide karta hai.

Moving Coil: Ek rectangular coil of wire ko magnetic field mein rakha jata hai. Ye coil ek lightweight aluminum frame par wound hota hai.

Spring: Coil ek pointer ke saath attached hota hai aur do control springs ke through permanent magnet ke poles ke beech suspended hota hai. Ye springs coil ki motion ko counteract karte hain.

Pointer and Scale: Coil ke saath attached pointer ek calibrated scale par move karta hai measurement indicate karne ke liye.

Hair Springs: Ye necessary control torque provide karte hain aur current leads ka kaam bhi karte hain.

2. Operation:
Jab electric current moving coil ke through pass hota hai, to ye coil ke ird-gird ek magnetic field generate karta hai.

Ye magnetic field permanent magnet ke magnetic field ke saath interact karta hai, aur ek torque produce hota hai jo coil ko rotate karne lagta hai.

Rotation (deflection) ka amount current ke proportional hota hai jo coil ke through pass ho raha hai.

Control springs ek counteracting torque provide karte hain, jo ensure karta hai ki pointer wahan ruk jaaye jahan current ke torque aur springs ke restoring torque balanced ho jaate hain.

Pointer calibrated scale par move karta hai, current (ya voltage) ka magnitude indicate karte hue.

3. Equation:
Pointer ka deflection diya ja sakta hai:
   \[
   \theta = kI
   \]
   jahan \(\theta\) angular deflection hai, \(I\) current hai, aur \(k\) proportionality constant hai.

Applications

Ammeters: Jab ammeters ke roop mein configure kiya jata hai, PMMC instruments direct current (DC) measure karte hain. Range extend karne ke liye ek shunt resistor use hota hai.

Voltmeters: Jab voltmeters ke roop mein configure kiya jata hai, ye voltage measure karte hain. Range extend karne ke liye ek series resistor use hota hai.

Galvanometers: Sensitive PMMC instruments ko galvanometers ke roop mein use kiya ja sakta hai small currents detect karne ke liye.

Advantages

High accuracy aur sensitivity.
Linear scale jo easy reading ke liye hota hai.
Low power consumption.
Aluminum frame ki wajah se good damping characteristics.

Disadvantages

Sirf DC measurements tak limited; AC measure nahi kar sakte bina rectification ke.
Delicate moving parts ki wajah se fragile construction.
Dusre types ke analog meters ke comparison mein relatively expensive.

PMMC instruments apni precision aur reliability ki wajah se bohot saare electrical measurement applications mein essential hote hain.

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