After learning how to build series and parallel circuits, your students will use ammeters and voltmeters to compare voltage and current flow so they can understand the similarities and differences between the two types of electrical circuits.
Each group will need:
Explain to your students the basic difference between series and parallel circuits:
Review the circuit diagram symbols on the first page of the “Investigating series and parallel circuits” worksheet with the students and clarify what the symbols represent.
Demonstrate for your students how an ammeter needs to be connected in the path of the moving electrons, so it becomes part of the circuit.
Also demonstrate how the voltmeter must be connected in parallel to the dry cell or the light bulb as the voltmeter creates a second pathway for the current to flow.
Put your students into groups and have them follow the instructions on their worksheets to build series and parallel circuits.
You may need to circulate among the groups to ensure the ammeters and voltmeters are being used correctly as students test circuits.
Remind your students to fill in their worksheet tables as they work through the steps of building the circuits.
After you’re done, gather the class and have the students share their data and observations. Encourage the students to ask questions and review their data before you have them complete the analysis section of the worksheet.
You can use the “Lab investigations and safety evaluation rubric” to guide your observation and assessment of your students during the activity.
1. a) In the series circuit, the current measurements did not change (or were very similar).
b) In the parallel circuit, the current measured through each branch was approximately half of the total current measured at the dry cells.
2. In the series circuit the voltage across the bulbs is 3.0 V, while in the parallel circuit it's 1.5 V.
3. Voltage across the bulbs is approximately half of the voltage across the dry cells. Adding the voltage across the two bulbs is equal to the total voltage of the circuit.
4. Current running through the bulbs is approximately half the current running through the dry cells. Adding the current in the bulbs in the parallel branches results in the total current of the circuit.
The paragraph should include:
In series circuits, there is a single path for electricity to flow through the circuit. The electrons must pass through each of the loads in the circuit on their way back to the source.
When devices such as light bulbs are connected in a series circuit, the current goes through each device in sequence. The current at each point in the circuit is the same, and each load in the circuit uses some portion of the total source voltage. Older model holiday lights which have only one wire are a good example of a series circuit. When one bulb burns out it stops the current, and the rest of the bulbs cannot light because the circuit has been interrupted.
When devices are connected in a parallel circuit, the current divides evenly along the paths available. The voltage across each load in a parallel circuit is the same.
An ammeter measures the amount of electric current at a point in a circuit. An ammeter should be connected in the path of the circuit. For example, to measure the current through a light bulb, an ammeter should be placed in series with, or in the same path as, the light bulb.
The relationship between voltage and current in circuits is:
In a series circuit, the current remains the same but the voltage changes.
A helpful way to remember this is: