13.1: Circuits and Circuit Diagrams
pg. 551
Key Concepts:
1. Circuits are a part of electrical technology. They can be connected in
series and in parallel.
- Circuit consist of; energy source, conducting wires, loads, and a switch.
- Circuit diagrams are a visual representation of an electrical circuit.
Circuit Diagram: a way of drawing an electric circuit using standard
symbols
- From a written description, you should be able to draw a circuit diagram
accurately, using the appropriate symbols.
- Current direction is also important and needs to be identified on the
diagram.
- For an electric cell the long line is a positive electrode and the shorter line
represents the negative electrode.
- When loads are added to a circuit diagram, they can either be attached in
series or parallel.
Table 1: Common Circuit Diagram Symbols
Series Circuit
Series Circuit: a circuit in which the leads are connected end to end so that
there is only one path for electrons to flow.
- Electrons can flow through only one path, in a continuous loop. If one load
shorts, then electrons can not flow through the rest of the circuit.
Figure 2: a) There is only one path for the electrons to follow in a series
circuit with two loads. The blue arrows show the direction of electron flow.
b) Circuit diagram for the circuit shown in a).
Parallel Circuit
Parallel Circuit: a circuit in which the loads are connected by branches so
that there are two or more paths for electrons to flow.
- In a parallel circuit, there is more then one path (two or more). Therefore if
on load shorts, electrons can still flow in one of the other pathways.
Figure 3: a) In this parallel circuit, there are two separate paths for the
electrons to follow with a single load in each path. b) Circuit diagram for the
circuit shown in a).
Sample Problem 1: Drawing Circuit Diagrams with Loads Connected in
Series
Draw a circuit diagram showing the electric cell, a switch, and three lamps
connected in series.
Step 1: Determine the circuit diagrams symbols for each device.
Step 2: Draw the loads (lamps) in series.
Step 3: Add the switch and electric cell. Remember to close the loop of the
circuit.
Sample Problem 2: Drawing Circuit Diagrams with Loads Connected in
Parallel
Draw a circuit showing a two cell battery with three lamps connected in
parallel. Include a switch for controlling each lamp.
Step 1: Determine the circuit diagram symbols for each device.
Step 2: Draw the lamps in parallel.
Step 3: Join the symbols together to close the loop of the circuit.
Evidence of Learning …. Students can
- identify and draw a series circuit.
- identify and draw a parallel circuit.
- determine the direction of flow and path of electrons in series and parallel
circuits.
- identify and use the various circuit symbols used to diagram a circuit.
Check Your Learning
Questions 1 – 7, page 554
Summary:
- Circuit can be represented using diagrams and circuit symbols
- Loads in a circuit may be connected in series or in parallel.
- There is only one path for electrons to follow in a series circuit, while in a
parallel circuit, there is more than one path.