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Measuring voltage and current in circuits

As we have seen in previous sections, an electric circuit is made up of a number of different components such as batteries, resistors andlight bulbs. There are devices to measure the properties of these components. These devices are called meters.

For example, one may be interested in measuring the amount of current flowing through a circuit using an ammeter or measuring the voltage provided by a battery using a voltmeter . In this section we will discuss the practical usage of voltmeters and ammeters.


A voltmeter is an instrument for measuring the voltage between two points in an electric circuit. In analogy with a water circuit, avoltmeter is like a meter designed to measure pressure difference. Since one is interested in measuring the voltage between twopoints in a circuit, a voltmeter must be connected in parallel with the portion of the circuit on which the measurement is made.

A voltmeter should be connected in parallel in a circuit.

[link] shows a voltmeter connected in parallel with a battery. The positive lead of the voltmeter must be connected closest to the positive end of the battery and the negative lead closest to the negative end of the battery. The voltmeter may also be used to measure thevoltage across a resistor or any other component of a circuit that has a voltage drop or potential difference.


An ammeter is an instrument used to measure the flow of electric current in a circuit. Since one is interested in measuring thecurrent flowing through the circuit, the ammeter must be connected in series with the measured circuit component ( [link] ). The positive lead from the ammeter must be connected closest to the positive end of the battery and the negative lead must be connected closest to the negative end of the battery.

An ammeter should be connected in series in a circuit.

Impact of meters on circuits

A good quality meter used correctly will not significantly change the values it is used to measure. This means that an ammeter hasvery low resistance so as to not slow down the flow of charge. A voltmeter has a very high resistance so that it does not add another parallel pathway to the circuit for the charge to flow along.

Investigation : using meters

If possible, connect meters in circuits to get used to how to use meters tomeasure electrical quantities. If the meters have more than one scale, always connect to the largest scale first so that the meter will not be damaged by having to measure values that exceed itslimits.

The table below summarises the use of each measuring instrument that we discussed and the way it should be connected to a circuitcomponent.

Instrument Measured Quantity Proper Connection
Voltmeter Voltage In Parallel
Ammeter Current In Series


The resistance of a circuit element can be thought of as how much it opposes the flow of electric current in the circuit.


The resistance of a conductor is defined as the potential difference across it divided by the current flowing though it. We use the symbol R to show resistance and it is measured in units called Ohms with the symbol Ω .

1 Ohm = 1 Volt Ampere .

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Physics - grade 10 [caps 2011]. OpenStax CNX. Jun 14, 2011 Download for free at http://cnx.org/content/col11298/1.3
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