Download An electric circuit

An electric circuit
An electric current (I) is mostly the flow of electrons (negatively charged particles) through a
material and thus a transfer of electric charge.
These negatively charged particles can only move
 in an electric field, which creates a difference in potential between two points (from a
point of high potential energy to one of low potential)
 if a continuous path is provided for them.
The path is called an electric circuit which basically consists of
 a source
 a load
 a switch
 a transmission system
Such a simple electric circuit can be seen in Figure 1 below:
battery
current (flow of
electrons)
switch
In order to make electrons move, a force must be applied to them. This is known as the
electromotive force (e.m.f.) or potential difference. Typical sources of emf are cells, batteries
and generators.
A load commonly converts the electrical energy from the source into some other forms of
energy. For instance, a lamp changes electrical energy into light and heat, or an electric motor
changes electrical energy into mechanical energy. So a load can be any electrical device.
A continuous path for the electrons to move is usually a loop of insulated copper wire,
because copper is a good conductor.
A switch is a component that breaks and closes the flow of current. For instance, when you
turn on a switch, it closes a gap in the circuit with a strip of conducting material, allowing the
current to flow. When the switch is turned off, the gap is opened again. This breaks the circuit
and stops the flow of current, because the air that fills the gap is an insulator.
In Fig.1 we have seen that depicting the various components in an electric circuit gets more
confusing and more complicated the more elements we have in a circuit. To simplify the
representation of the circuit, fixed graphical symbols are used. Figure 2 below shows a few
examples of symbol standardisation.
Wire
Connection between wires
Battery
Light bulb
Switch
List of words:
electric current – elektrischer Strom
charge – die Ladung
thus – folglich
particles – Teilchen
elctric field – elektrische Feld
to create – schaffen, bilden, herstellen
potential difference – Potenzialdifferenz
continuous – dauerhaft
to provide – bereit stellen
electric circuit – Stromkreis
path – Pfad, Weg
source – die Quelle
load – der Verbraucher
transmission system – Übertragungssystem
wire – der Draht
switch – der Schalter
force – die Kraft
to apply – anlegen
electromotive force – elektromotorische Kraft
cell – nicht wiederaufladbare Batterie
to convert – umwandeln
mechanical energy – mechanische Energie
device – Gerät, Vorrichtung
loop – Schleife
insulated – isoliert
copper – Kupfer
conductor – Leiter
component – Bauelement, Bestandteil
to break – unterbrechen
gap – die Lücke, der Freiraum
a strip – ein Streifen
insulator – Isolator
depict – darstellen
various – verschiedenartig
to simplify – vereinfachen
standardisation - Normung
Activities:
I)Answer the following questions on the basis of the impulse text.
1)How is electric current defined?
2)What are electrons?
3)What does emf stand for and what is it needed for?
4)Where do electrons move?
5)What different parts does an electric circuit consist of?
6)What is the function of each component in an electric circuit? Give an example each!
II)On the basis of Figure 1 draw a simple circuit by using the standard symbols, which are
represented in Figure 2.
III)Hands-on activity
a)Build a simple electric circuit with the materials/components given.
b)Write down the instructions!
c)Present your circuit board!
IV)Match the words on the left with the definitions on the right! (could even be done as a crossword
on the basis of HotPotatoes)
electric current –
charge –
particles –
an electric field –
continuous –
to provide –
an electric circuit –
a source –
a load –
a battery –
to convert –
transmission system –
device –
to insulate –
copper –
conductor –
component –
to break –
a gap –
insulator –
a material where electrons can easily flow
it is a path where electricity goes through
any space; nothing in between
it can be re-charged, an accumulator
to open, to turn off
to cover wires
the flow of electrons
property of electrons and protons
connecting wires
permanent
to supply
a material where electrons can hardly flow
an ………… …………. is caused by charged
particles
conducting metal
it converts one form of energy into another
one
very small parts
emf is provided by a …………..
to change into another state
an essential part of an electric circuit
a load can be any electrical ………………
Sources:
Electricity Usborne Publishing Ltd, 1991, ISBN 0860200787
Science and Technology Oxford University Press ISBN 0199101434