# 13.2 Current and measurement  (Page 2/2)

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How much charge flows per second in a circuit with a current of $1,5\phantom{\rule{2pt}{0ex}}\mathrm{A}$ ?

1. Asked for: Charge, Q

Given: Current $I=1,5\phantom{\rule{2pt}{0ex}}\mathrm{A}$

$\Delta t=1\phantom{\rule{2pt}{0ex}}\mathrm{s}$

2. $I=\frac{Q}{\Delta t}$
3. $\begin{array}{ccc}\hfill Q& =& I×\Delta t\hfill \\ & =& \hfill 1,5\phantom{\rule{2pt}{0ex}}\mathrm{A}×1\phantom{\rule{2pt}{0ex}}\mathrm{s}\\ & =& 1,5\phantom{\rule{2pt}{0ex}}\mathrm{C}\hfill \end{array}$

If $500×{10}^{3}\phantom{\rule{2pt}{0ex}}\mathrm{\mu C}$ of charge flow past a point in a circuit in 1 second, what is the current in the circuit?

1. Asked for: current, I

Given: charge $Q=500×{10}^{3}\phantom{\rule{2pt}{0ex}}\mathrm{\mu C}$
$\Delta t=1\phantom{\rule{2pt}{0ex}}s$

2. $\begin{array}{}Q=500×{10}^{3}\mathrm{\mu C}\\ \phantom{x}=500×{10}^{3}×{10}^{-6}\mathrm{C}\\ \phantom{x}=0,5\mathrm{C}\end{array}$

3. $I=\frac{Q}{\Delta t}$

4. $\begin{array}{}I=\frac{Q}{\Delta t}\\ \phantom{x}=\frac{0,5\mathrm{C}}{1\mathrm{s}}\\ \phantom{x}=0,5A\end{array}$

I measure the current in a circuit to be $500\mathrm{mA}$ . How much charge is flowing per second in the circuit?

1. Asked for: Charge, Q

Given: Current $I=500\mathrm{mA}$ ,
$\Delta t=1\mathrm{s}$

2. $500\mathrm{mA}=500×{10}^{-3}\mathrm{A}$

3. $I=\frac{Q}{\Delta t}$

4. $\begin{array}{}Q=I×\Delta t\\ \phantom{x}=500×{10}^{-3}\mathrm{A}×1\mathrm{s}\\ \phantom{x}=0,5\phantom{\rule{2pt}{0ex}}\mathrm{C}\end{array}$

## 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.

## Voltmeter

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.

[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.

## Ammeter

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.

## 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

#### Questions & Answers

where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is
Properties of longitudinal waves