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Natural sciences

Grade 8

Energy: electicity, heat and light

Module 5

Electric circuits

An electric circuit consists of:

a source – cell (battery or cells)

conductors – wires

a switch – control point

other components like light bulbs, resistors and measuring instruments.

a Battery is a collection of cells.

Activity

To investigate the different components in a circuit and the symbols used to represent them [lo 2.3]

Assignment 1:

Draw a simple sketch of a single torch cell. One end has a protrusion, this is the positive pole. The opposite end is the negative pole. Add the labels “positive pole”, “negative pole”.

Now draw three more torch cells in a battery, as they would be placed in the shaft of a torch – what do you notice about the positive and negative poles.

This forms a battery and the cells are linked in series.

Assessment of Sketch

Were you able to draw the sketch and add labels correctly?

[LO 2.3]

Drawing a number of components is time consuming and cumbersome. Using symbols saves time. These symbols are used internationally!

following symbols are used:

A length of copper wire is represented by means of a line

A light bulb is represented by means of:

A cell (the long thin line is the +)

An ammeter (to measure the strength of the current)

A switch : Open:

Closed:

A current diagram will always contain these components (parts). When we place all the components one after the other they are in series.

The diagram is always drawn in the form of a square. A simple circuit diagram will be drawn as follows.

Components can also be linked in parallel, as shown below.

Assignment 2:

Now draw three light bulbs that are linked in parallel – make use of symbols.

In a parallel linkage, the current is divided. If one of the light bulbs breaks the others will continue to glow!

The light bulbs in you home are mostly in ________________________________.

Assessment of Sketch

Were you able to draw the sketch and add labels correctly?

[LO 2.4]

Assessment

LO 2: Constructing Science Knowledge:

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

This is evident when the learner:

  • interprets information;

Memorandum

Assignment 1:

An electric circuit comprises:

1. An electrical point and closed circuits.

2. A source – cell or battery

conductors – wires

a switch – controlling point

other components like light bulbs, resistors and measuring instruments.

cellbattery

Positive cellpool

A Battery is a collection of cells.

Drawing a number of components may be a nuisance and time-consuming. You need symbols that could provide shortcuts. Scientists have fortunately devised these already and they are used internationally!

A length of copper wire is represented by means of a line

A light bulb is represented by means of:

A cell (the long thin line is the +)

An ammeter (to measure the strength of the current)

A switch

Assignment 2:

  • A circuit diagram always contains these components (or parts) of the current.
  • To begin, we arrange the components in line – this is known as "in series".
  • The diagram is always drawn in the form of a square. A typical diagram is shown as:

A circuit diagram of three cells in series, an open switch, two light bulbs in series and an ammeter.

The concept of connection/linking in parallel may be difficult to understand. In the case of cells it can be shown as:

ELECTRICITY AND ITS USES IN THE HOME

THE LIGHT BULB:

  • We'll begin with the light bulb. We have said that the light bulb represents ineffective utilisation of electric power. This is because 95 of the 100J are lost to heat and only 5J go towards light energy.
  • We therefore need to think of a more economical means for lighting. But before we can investigate the issue further, we need to know what a typical light bulb consists of.
  • The light bulb comprises a glass bulb filled with a particular gas, which isn't oxygen.
  • The light bulb comprises a glass bulb filled with a particular gas, which isn't oxygen.

Why not? Wait and see. The wires inside a light bulb are wound up in small spirals. They are actually made of a particular metal filament (tungsten) that has resistance. This means that it tries to block the current and therefore becomes extremely hot. The heat is so intense that it begins to glow and becomes white hot! If the glass bulb were to be filled with oxygen, the intensity of the heat would melt everything. But the hollow is filled with a stable gas – Argon.

FLUORESCENT LIGHTS AND ECO-LAMPS:

Fluorescent lights (neon lights) are used in many offices and schools, as well as in some homes. They are filled with a particular gas and are lined with a chemical substance that emits light when an electric current passes through the tube. Fluorescent lights do not build up much heat, which reveals something of their effectiveness.

Eco-lamps: As we pay for our electricity, and also because electricity supply is limited, it is important for consumers to have electrical appliances that utilise electricity effectively. Fluorescent lights and eco-lamps do cost more, but they last much longer.

Questions & Answers

how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Natural sciences grade 8. OpenStax CNX. Sep 12, 2009 Download for free at http://cnx.org/content/col11050/1.1
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