learning goals

Be able to construct a series and a parallel circuit in a model.
Understand that as lights are added to a series circuit, the brightness of each is reduced, whereas this is not true in a parallel circuit. (note: a constant voltage source is assumed.)
Understand that in a series circuit, removing any element breaks the circuit.
Understand that in a parallel circuit, removing any element does not affect the circuit of the other elements.
(Note: the concept of voltage is not presented here.)

Discovery question

How do you design a circuit that will light up several bulbs?
!Cannot resolve external resource into attachment.
Use a computer model to build a circuit to light two holiday lights with a battery.

Engage

Holiday lights are many small light bulbs in a long string. Each one isn't nearly as bright as a regular light bulb. How do you think they are connected together?

Imagine that you have 10 lights and a battery. How would you connect them so that they all light up with the same brightness? Use the drawing tool and stamps to make a circuit with 10 lights and a battery.

DRAWING TOOL, BATTERY STAMP, LIGHTS STAMP

Explore

With the Circuit Construction Kit below, you can build a model of a circuit. You can see if it works and test the voltage between any two points in the circuit.

Drag two wires, a battery, and a light bulb into the blue workspace.

!Cannot resolve external resource into attachment.

You can connect the pieces any way you want. Drag the ends (junctions) together to connect them.

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You can disconnect the junctions by right-clicking on the junction and choosing "split junction".

!Cannot resolve external resource into attachment.

Try to construct a circuit that lights the bulb with the battery. If you succeed, the light will glow and the round balls (representing charges) will move around the circuit.
CCK MODEL

When you succeed, take a snapshot of your circuit.

Describe in words how you made the circuit work.
ANSWER BOX

Drag another light bulb into the blue workspace. Try to construct a circuit that will light both light bulbs. You can also drag in more wires if you need them. When you succeed, take a snapshot of your circuit.

Describe in words how you made the circuit work.
ANSWER BOX

Explain

There are two ways to connect light bulbs in a circuit:

• In series means "one after the other". Here is a diagram of light bulbs in series.

!Cannot resolve external resource into attachment.

• In parallel means "side by side". Here is a diagram of light bulbs in parallel.

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Which kind of circuit is the one you made?
o series
o parallel

Explain why you think so.

A key difference between the two types is this:

• If one light is removed from a series circuit, the other one won't work.
• If one light is removed from a parallel circuit, the other one will still work.

Use this rule to test if your two-light circuit is a series or a parallel circuit. Explain what you discover.
ANSWER BOX

Elaborate

Here is the Circuit Construction Kit again. If you made a series circuit before, now make a circuit with the lights in parallel. If you made a parallel circuit before, now make a circuit with the lights in series.
When you succeed take a snapshot of your circuit.

CCK MODEL

Evaluate

Think about all the lights and appliances in your house. Which kind of circuit do you think they are in?
o series
o parallel
Why do you think so?
ANSWER BOX

Think about all the lights and appliances in your house. Which kind of circuit do you think they are in?
o series
o parallel
Why do you think so?
ANSWER BOX

If you have already done the activity Build a circuit, answer the questions below.

Compare your model circuit with your real circuit. Are they the same?
ANSWER BOX

Which is more fun to work with, the circuit model or the real circuit?
ANSWER BOX