1. Home
  2. Siyavula textbooks: grade 10
  3. Electric circuits
  4. Current and measurement

13.2 Current and measurement  (Page 2/2)

<< Chapter < Page
  Siyavula textbooks: grade 10     Page 2 / 2
Chapter >> Page >

How much charge flows per second in a circuit with a current of 1,5 A ?

  1. Asked for: Charge, Q

    Given: Current I = 1,5 A

    Δ t = 1 s

  2. I = Q Δ t I = {Q} over {%DELTA t}

  3. Q = I × Δ t = 1,5 A × 1 s = 1,5 C

If 500 × 10 3 μC 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 μC
    Δ t = 1 s

  2. Q = 500 × 10 3 μC x = 500 × 10 3 × 10 − 6 C x = 0,5 C

  3. I = Q Δ t

  4. I = Q Δ t x = 0,5 C 1 s x = 0,5 A

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

  1. Asked for: Charge, Q

    Given: Current I = 500 mA ,
    Δ t = 1 s

  2. 500 mA = 500 × 10 − 3 A

  3. I = Q Δ t I = {Q} over {%DELTA t}

  4. Q = I × Δ t x = 500 × 10 − 3 A × 1 s x = 0,5 C

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.

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.

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.

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

Questions & Answers

why we learn economics ? Explain briefly
ayalew Reply
why we learn economics ?
ayalew
why we learn economics
ayalew
profit maximize for monopolistically?
Usman Reply
what kind of demand curve under monopoly?
Mik Reply
what is the difference between inflation and scarcity ?
Abdu Reply
What stops oligopolists from acting together as a monopolist and earning the highest possible level of profits?
Mik
why economics is difficult for 2nd school students.
Siraj Reply
what does mean opportunity cost?
Aster Reply
what is poetive effect of population growth
Solomon Reply
what is inflation
Nasir Reply
what is demand
Eleni
what is economics
IMLAN Reply
economics theory describes individual behavior as the result of a process of optimization under constraints the objective to be reached being determined by
Kalkidan
Economics is a branch of social science that deal with How to wise use of resource ,s
Kassie
need
WARKISA
Economic Needs: In economics, needs are goods or services that are necessary for maintaining a certain standard of living. This includes things like healthcare, education, and transportation.
Kalkidan
What is demand and supply
EMPEROR Reply
deman means?
Alex
what is supply?
Alex
ex play supply?
Alex
Money market is a branch or segment of financial market where short-term debt instruments are traded upon. The instruments in this market includes Treasury bills, Bonds, Commercial Papers, Call money among other.
murana Reply
good
Kayode
what is money market
umar Reply
Examine the distinction between theory of comparative cost Advantage and theory of factor proportion
Fatima Reply
What is inflation
Bright Reply
a general and ongoing rise in the level of prices in an economy
AI-Robot
What are the factors that affect demand for a commodity
Florence Reply
price
Kenu
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
<< Chapter < Page Page > Chapter >>

Read also:

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Siyavula textbooks: grade 10 physical science [caps]. OpenStax CNX. Sep 30, 2011 Download for free at http://cnx.org/content/col11305/1.7
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 10 physical science [caps]' conversation and receive update notifications?

Ask