| Intermediate Technology Education | Energy and Power Technology | Pre-Design | Topic 3 | Activity 10 |
This activity covers the following
An electric circuit is a closed path that electrons can flow through. All electric circuits have four basic components
A pictorial drawing of a simple circuit is shown below.
Most of the time, it is not convenient to make pictorial drawings of electric circuits. Instead, a type of drawing called a schematic is used. From previous activities, you should recall that we use letters as symbols to represent voltage, current, resistance and power. For schematic drawings we use a different set of symbols. A few basic ones are shown below.
Using schematic symbols, the circuit drawn above as a pictorial would look like the figure below. As you can see, the drawing is much simpler. It is also easier to draw, and easier to read.
Look at the next schematic. Can you identify the components in the circuit?
The following pictorial shows two lights connected in series. Components connected in series means that electrons flow through one and then the other, losing some of its energy to each one. In the case of the lights, each light will be less bright than if there was only one light in the circuit.
As the schematic below shows, the electrons flowing through the circuit have to pass through the two lights in sequence.
The next pictorial shows two lights connected in parallel. There are separate paths for electrons to flow through each light. As a result the lights are full brightness.
The parallel circuit schematic shows the two paths for current flow in the circuit.
The previous activity introduced EMF, current and resistance measurements (voltage, amperes, and ohms respectively). It also showed that the three had the mathematical relationship of
EMF (in volts) = Current (in amps) × resistance (in ohms)
and that this relationship is, in fact, called Ohm's Law.
To measure electrical quantities, we commonly use a multimeter, of the type supplied for this course. If you are unfamiliar with the use of a multimeter, complete the activity Using a Multimeter before completing the remainder of the activity.
For additional information on these topics, please check these web sites
When you are ready, move to Your Turn