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Rev. Notes > IGCSE > Elecrical Quantities
Previous Topic Elecrical Quantities Next Topic

Electric charge One Coulomb Charge Production of electric charge
Detection of electric charge Experiment to detect the electric charge Electrical conductors and insulators
Electric field Electrostatic forces Application of electrostatic forces
Electric current One Ampere of electric current Direction of electric current
Basic relation of electric current Direct current Alternating current
Ammeter Electromotive force - (e.m.f.) Potential difference
One Volt Explanation of potential difference Measurement of potential difference
Voltmeter Resistance Affect of length of the conductor on resistance
Affect of cross-sectional area on resistance Affect of temeprature on resistance How nature of material affects the eresistance
Ohm's law Potential difference - Current graph for Ohmic conductors Potential difference - Current graph for tungsten filament
Potential difference - Current graph for semiconductor diode Electrical energy Formula for electrical energy
Electrical Power Formulae for electrical power


Ammeter is an intrument used to measure current.

It’s basically a galvanometer which is modified to measure current. A galvanometer will give full scale deflection with very samll current of few milliamperes or micro-amperes. So it can not be directly used to measure heavier currents.
To measure heavier currents a low resistence is connected parallel to galvanometer. Then it becomes ammeter. The low resistance so connected is called shunt. The shunt provides an alternate path to flow of current since its resistance is low most of the current passes through it and only a small fration of current passes through galvanometer. However the deflection in galvanometer will be proportional to the total current because if the total current is increased its fraction through galvanometer will also increase and there will be greater deflection.
By using shunt resistances of different suitable values , the ammeters of different ranges of current can be made by same galvanometer.
 The ammeter is always connected in series in the circuit to measure current in that circuit.





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View Comments on this Chapter - Total Comments (6)
sree Said :
wish these had a diagrams
  24/12/15 10:01 AM
student 567 Said :
There are no diagrams, but seeing that you don't give a shit... why should i bother to comment?! Can you just put the dam diagram up already!
  18/04/14 08:10 PM
Deepak varun Said :
there is a spelling mistake to say said they said asaid please change it admin
  17/11/13 06:26 AM
gargi sachdev Said :
diagrams aren't there ...
  29/08/12 12:35 AM
gargi sachdev Said :
diagrams aren't there ...
  29/08/12 12:35 AM
Ajay Said :
I cant see any diagrams? can u help me with it
------------------------------------------------------------------------------------- Admin Replied:

Hi Ajay, thank you for informing us about this issue. We will make sure we make those images available for you as soon as possible.

Thank you

  15/03/12 12:13 PM


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