Lesson Notes
Physical Sciences Grade 10
LESSON
Potential Difference and ResistanceTeacher Guide
3
Working with Circuit Diagrams
Circuit diagrams show how to connect the components in a circuit. The components are the different parts used to
make a circuit. Each type of component is represented by a different symbol. Circuit diagrams and symbols make
it a lot easier to draw and understand electric circuits. In this lesson we will work from circuit diagrams to build the
circuits. We will also take readings of potential difference and current at various points in the circuit..
Lesson Outcomes
By the end of this lesson, learners should be able to:
• Construct and interpret circuit diagrams
• Measure current and potential differences in a series
circuit
Lesson Notes
We always construct an electrical circuit from a design
plan which we call a circuit diagram. Symbols are used to
denote the components and lines denote the connectors.
You must be able to draw and identify circuit symbols, so
here they are:
NAME
IMAGE
Curriculum Links
LO 1: Scientific Inquiry and Problem-solving Skills
AS 1: Conduct an investigation
AS 2: Interpret data
The battery is connected to a switch and to a light bulb.
Below is a circuit diagram for the torch:
SYMBOL
Cell
Bulb
Resister
Using the circuit, we can measure the current (I1) passing
into the light bulb, the current (I2) passing out of it and
the p.d. (V) across the bulb. To do this we connect two
ammeters and a voltmeter into the circuit
I1
Variable
resister
Switch (Open)
Switch
(Closed)
Ammeter
Voltmeter
Components can be connected in two ways, either in
series or in parallel. Series means one component is
followed by the next one to form a single loop. Parallel
means the components are placed alongside or parallel
to each other.
An electric torch consists of a battery made up of two
torch cells (the cells are connected in series with the
positive terminal of one cell connected to the negative
terminal of the second cell).
103
I2
and get the following readings:
I1 (A)
I2 (A)
V (V)
0,16
0,16
2,9
The readings on ammeters 1 and 2 are the same. We
therefore know that the current is the same throughout
the circuit.
?
TASK
Draw a circuit diagram of a simple series circuit
that consists of two cells, a switch, a resistor and a
light bulb. Also draw in a voltmeter that measures
the potential difference across the light bulb.