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Rev. Notes > IGCSE > Elecrical Quantities
 
 
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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
 

Voltmeter

Voltmeter is an instrument used to measure potential diference across a resistor or between any two points in a in a circuit.

A voltmeter is always connected in parallel to a resistor or device across which potential difference is to be measured because potential difference across all components (resistors voltmeter etc.) connected between same two points would be same.

Voltmeter is basically a galvanometer which is modified to measure potential difference. A galvanometer is converted into voltmeter by connecting a high resistance in series with it. Then the total resistance of voltmeter will be very high According to Ohm's law

V=IR or I = v / R

Since potential difference ' V ' across voltemeter and resistors across which it is connected will be same, current drawn by it will be small as it has high resistance. This current will produce sufficient defection in voltmeter (or the galvanometer used in it).

This deflection will be proportional to the current passing through it and hence to potential differenc across it. By connecting high resistances of differenet siutable values in series with galvanometer, it can be converted into voltmeters of different ranges.

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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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