Electrical Measuring Instruments Notes by Sir Waqar Hussain

Important Easy Notes of Physics of Chapter No. 15: Electrical Measuring Instruments  written by Professor Mr. Waqar Hussain Suib. These notes are very helpful in the preparation of Physics for students of the 12th class and these are according to the paper patterns of all Sindh Book Boards.

Summary and Contents:
Topics which are discussed in the notes are given below:
  • State and Explain The Moving Coil Galvanometer with its Principle, Construction and Working.
  • Current Sensitivity of Galvanometer
  • To Increase Sensitivity of Galvanometer
  • What is Ammeter?
  • Conversion Of Galvanometer Into Ammeter
  • Mathematical Expression for Shunt Resistance(𝑹𝒔 )
  • What is Multi Range Ammeter?
  • What is Voltmeter?
  • Conversion of Galvanometer into Voltmeter
  • What is Multiage Voltmeter?
  • State and Explain Wheat Stone Bridge with its Working
  • State and Explain Meter Bridge with its Working
  • State and Explain POST OFFICE BOX [P.O BOX]
  • State and Explain POTENTIOMETER with its Working
  • A moving coil galvanometer has a resistance of 50 ohms and it given a full-scale deflection for P.D of 150 mV. What should be the resistance of the shunt used with the galvanometer in order to use it as an ammeter reading up to 4 amperes? 
  • A galvanometer of resistance of 50Ω gives full-scale deflection with a current of 0.005 amperes. How will you convert it into an ammeter measuring maximum current of 1.0 ampere?
  • A galvanometer of resistance 60Ω given full-scale deflection with a current of 4mA, a resistance of 10940 Ω is connected in series with the coil to convert it into voltmeter; find the range of voltmeter obtained. 
  • A moving coil galvanometer has a resistance of 25Ω, and it gives a full-scale deflection for a P.D. of 50 mV. If the galvanometer is to be converted into a voltmeter reading up to 50 volts, what should be the resistance of the series resistor?
  • A moving coil galvanometer has a resistance of 50Ω, and it gives a full-scale deflection for a P.D. of 100 mV. If the galvanometer is to be converted into a voltmeter reading up to 50 volts, what should be the resistance of the series resistor?
  • The coil of a Galvanometer having a resistance of 50 ohms and a current of 500 micro-amperes produces a full-scale deflection in it. Compute: a) The shunt required to convert it into an ammeter of 5 amperes range. b) The series resistance required to convert it into a voltmeter of 300-volt range.
  • An ammeter deflects full-scale with a current of 5 amperes and has a total resistance of 0.5 ohm. What shunt resistance must be connected to it to measure full scale current up to 30 amperes?
  • A 300 volts’ voltmeter has a total resistance of 20 kilo-ohms. What additional resistance is required to convert it into a voltmeter, reading up to a maximum of 600 volts?
  • A 250-volt voltmeter has a total resistance of 20,000Ω. What additional series resistance must be connected to it to increase its range to 400 volts?
  • A maximum 50 milli-ampere current can be allowed to flow through a 19.8ohm coil of a galvanometer. The galvanometer is to be used to measure 5-ampere maximum current. Calculate the length of a copper wire to be used as a shunt. The diameter of the wire is 4mm; the specific resistance (ρ) of copper is 1.6 x 10–8 ohm-m.
  • An ammeter deflects full-scale with a voltage of 2.5 volts, and has a total resistance of 0.5Ω. What small resistance must be connected to measure 20A full-scale?
  • A 300 volts voltmeter has a total resistance of 20 kilo-ohms. What additional resistance is required to convert it into a voltmeter, reading up to a maximum of 600 volts?
  • galvanometer has a resistance of 100 ohms. A difference of potential of 50mV gives the full-scale deflection. Calculate the shunt resistance to read from 0–5A. What is the value of the series resistance if the galvanometer is to be converted into a voltmeter to read up to 250V?
  • A galvanometer whose resistance is 50Ω deflects full-scale for a potential difference 100 mV across its terminals. How can it be converted into a voltmeter of 50V range? 
  • A galvanometer of resistance of 50 ohms gives full scale deflection with a current of 10 mA. A shunt of 0.05 ohm is connected in parallel to convert it into an ammeter. Find the range of the ammeter
  • A voltmeter measuring up to 200 V has a total resistance of 20000 ohms. What additional series resistance must be connected to it to increase its range to 600V?
  • A galvanometer having resistance 50Ω, deflects full scale for a potential difference of 100 mV across the terminals. What resistance should be connected in series to increase its range to 50V?
  • A galvanometer of resistance of 60Ω gives deflects full-scale for a potential difference of 100 mili-volts across its terminals. What shunt resistance must be connected to convert it into an ammeter of 5 ampere range? 

Loading your document...

Download PDF