Download INTRODUCTION TO ELECTRICITY Name

WORKSHEET: Current Electricity & Electric
NAME:
Circuits – An Introduction
Static electricity is a build-up of electric charge that remains stationary (e.g. at the end of a charged
rod). If, somehow, this electricity can be made to move you have current electricity or an electric
current. We now know that current in a conducting solid is a flow of negatively charged electrons.
Current electricity can be used to make a variety of useful changes (e.g. it can create light as in a
light globe).
What is a circuit?
An electric circuit is a pathway along which electrons flow. All circuits require three basic
components:
1.
2.
3.
An energy source- battery, power source- provides energy to push the electrons around
the circuit.
A conducting pathway- there has to a pathway for the electrons to flow. A closed
circuit is required for the light to glow. If there is a gap in the pathway then the circuit is
open and the light will not glow.
A load to give the circuit a purpose (i.e. something that transforms the electrical energy
into another useful form of energy) e.g. light bulb transforms electrical energy into light
energy and some heat energy.
For a circuit to work (eg for a light globe to glow), the circuit must be complete. This means there
must be an unbroken pathway from one terminal of the power supply, through the globe, and back
to the other end.
ACTIVITY 1
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Use Clickview to view “Electricity – how it works”
Complete the diagram below adding your own words for each caption.
The wires ….
The lamp….
The power
source….
Electrons are….
ACTIVITY 2
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View the Brainpop: Electric Circuits
Complete the following questions.
1.
In the space below, record FIVE important scientific facts you learnt from this movie.
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2.
Do the online quiz and record your score.
ACTIVITY 3
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View the Brainpop: Electricity
Complete the following questions.
1.
In the space below, record FIVE important scientific facts you learnt from this movie.
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2.
Do the online quiz and record your score.
ACTIVITY 4: Understanding some electrical terms: Current,
Resistance & Voltage
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View the Brainpop: Current
Complete the table below.
Electrical term
Definition
Abbreviated
symbol
Unit and Symbol used
to measure quantity.
Current
Resistance
Voltage
ACTIVITY 5: Using an Analogy to Understand Electrical Circuits
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Visit http://faraday.physics.utoronto.ca/IYearLab/Intros/DCI/Flash/WaterAnalogy.html to
view a comparision between a DC circuit and a water circuit.
Analogies can be used to help us understand the
components of an electric circuit. An analogy uses
an everyday example that has many similarities to
a concept or idea that is more abstract and difficult
to understand.
In the diagram below, an analogy between a
simple electric circuit and a water system is
summarised.
In the water system shown opposite, a pump
provides pressure to move the water the reservoir
upwards against the force of gravity. Water at the
highest point has stored potential energy. It moves
through the pipes under pressure and then travels
downwards. Moving downwards freely (due to
gravity) its stored potential energy changes to
kinetic energy. The water wheel interferes with
the natural flow of water, and the kinetic energy
of the water is transferred to kinetic energy of the
wheel. Finally, the water flows into the reservoir
at the bottom, now low in potential and kinetic
energy and the cycle starts again.
So how does this relate to a circuit?
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Complete the table below by using the text on the previous page and the diagrams above.
Part of the Water
System
Water
Pipes
Valve
Water Wheel
Pump
Corresponding (analogous)
part of the electrical circuit
How they relate to each other

Complete the following question.
What are the benefits of using the analogy of the water system as a model to help understand the
movement of charge in an electrical circuit? Does the analogy have any limitations (problems).
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ACTIVITY 6: Circuit Symbols

Draw a symbol and describe the function of the following electric component.
Circuit component
Variable Power Source
(eg on 2V)
Battery (eg 12V)
Conducting Wire
Switch- open
Switch-closed
Light Bulb
Resistor
Variable Resistor
Ammeter
Voltmeter
Symbol
Function
ACTIVITY 7: Drawing Circuits
Scientists use circuit symbols and follow a common set of rules to draw electric circuits to simplify
the circuits and aid in effective communication.
When drawing diagrams, try to follow these guidelines:
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GUIDELINES FOR DRAWING CIRCUIT DIAGRAMS
Draw in pencil (this makes erasing errors easy)
Use straight lines to connect all components.
Use the correct circuit symbols.
Make each diagram large enough to see clearly
Following the above guidelines, draw circuit diagrams for each of the following circuits.
Picture of circuit
The globe is not glowing.
Each globe is glowing.
Each globe is glowing.
Circuit Diagram
Picture of circuit
Circuit Diagram
6
‘
‘R’ Represents a fixed resistor
7.
Each globe is not glowing and the meter is an ammeter
ACTIVITY 8: Current & Voltage - Extension
WHAT EXACTLY IS AN AMP?
You will have learned that an amp is the unit for electric current. Current is the rate of flow of
charge. But what is an amp equivalent to?
The symbol to abbreviate charge is q.
Scientists measure charge in units called the Coulomb (C). One lone electron actually carries a tiny
charge. 1C of charge is equal to the charge on 6.25 billion electrons!
The formula linking current, charge and time is:
Current = Charge flowing/time
OR
I = q/t
Therefore, when a current of 1 amp is measured in a circuit, this is equivalent to 1C of charge
passing a point in a circuit every second. Thus a current of 3A means 3C of charge is flowing every
second.
Note: The above equation is often written as:
q=Ixt
VOLTS
A volt is the unit to measure voltage or potential difference. Voltage is defined as the change in
energy that occurs when charge moves from one place to another in a circuit.
The unit for energy is the JOULE (J). It follows from the above definition that voltage can be
found using the relationship:
Voltage = Change In Energy/ Charge
Thus 1 volt is equivalent to a change in energy of 1J per coulomb of charge.
If a battery supplies a voltage of 12V, this means each C of charge gains 12J of energy as it passes
through the battery.