DC Circuits; Batteries, Bulbs and Beyond

Author(s): Seth Bush
Subject: Physics
Grade Level(s): Grade 4
Big Idea(s):

Students know how to design and build simple senes and parallel circuits by usmg
components such as wires, batteries, and bulbs.
Students know electrical energy can be converted to heat, light, and motion.
Students know how to predict the voltage or current in simple direct current (DC) electric circuits constructed from batteries, wires, resistors, and capacitors.

What you need: • DC circuit component kit
• Bread-board
Setting: Classroom
Time Needed: Teacher’s Discretion

Summary:

In this activity we will construct a number of DC circuits using our test bread-boards. We will remake our flashlights. We will make parallel and series circuits with batteries, bulbs, resistors and simple electric motors.

Learning Goals / Objectives:

1.) Students will learn about DC circuits by making them and testing them. In particular, students will explore:
• Open vs Closed circuits
• Circuits with devices in series and in parallel
• Circuits with resistors in series and in parallel
• Circuits with batteries in series and in parallel
• Short circuits

Background

This activity is looooong. It could easily be broken up into a series of small activities that could be accomplished over many days. Getting quantitative with and adding resistors in parallel to determine total resistance is a good way to get students to add fractions in a real world context.

Safety
This activity has little to no risk associated with it. Students may be a little apprehensive, thinking they may get a shock from the battery. They will not be shocked by a D cell or any other 1.5 V battery. Batteries may get warm when in operation.

Setup:

Make sure you have the following:
• DC circuit component kits
• Bread-boards
• Patience

Anticipatory Set:

Driving Questions
1. What is a circuit? Open? Closed? Short?
2. What does a battery do?
3. What does it mean to have devices: in parallel? in series?

Instructions / Activities:

Part A: Bread-Board Flashlight
1. Using your DC circuit components and bread-board, rebuild the flashlight you originally made in the “Flashlight Challenge”. Sketch a circuit diagram for your bread-board flashlight in your notebook.
Optional: Use your multimeter to measure and record:
a. ΔV, I and R for each leg of the circuit.
b. What is ΔV tor the whole circuit?
c. Does I change as you go around the circuit?

2. Add a single pole switch, so you can turn your flash light on and off. Sketch a circuit diagram with the switch in your notebook.
Optional: Use your multimeter to repeat the measurements in la with
a. The switch open. (Open circuit)
b. The switch closed. (Closed circuit)
c. Can you explain your observations?
d. Can you make a general claim about open circuits?

3. Consider the circuit diagram depicted on the right. BEFORE building the circuit make a few predictions. What will happen to the bulb when:
a. Switch 1 is closed and Switch 2 is open?
b. Switch 1 is open and Switch 2 is closed?
c. Switch 1 is closed and Switch 2 is closed?

4. Adjust the switches to test your predictions in 3a, b, and c. Record your observations in your notebook. Can you explain your observations? Any surprises?

Part B: Parallel and Series
For each circuit in the part of the activity, we are going to follow a Think, Do, Understand, Grow approach. We will:
a. Make predictions
b. Build the circuit to test our predictions
c. Explain our observations and assess the accuracy of our original predictions
d. Make deductions based on your observations

5. Consider the circuit diagram with two bulbs in series depicted on the right.
a. Which of the following do you predict will occur when the switch is closed?
i. Bulb 1 will be brighter than Bulb 2.
ii. Bulb 2 will be brighter than Bulb 1.
iii. Bulbs 1 and 2 have roughly the same brightness.
b. Make the circuit. What do you see? Record your observations.
c. Can you explain your observations? Do they match your prediction?
d. From your observation, what can you say about the Bulbs in series for 5. current felt in Bulb 1 vs current in Bulb 2? (To feel smug, test your deduction with a multimeter).
e. Draw an alternative circuit diagram that depicts the same circuit.

6. Consider the circuit diagram with two bulbs in parallel depicted on the right.
a. Which of the following to you predict will occur when the switch is closed?
i. Bulb 1 will be brighter than Bulb 2.
ii. Bulb 2 will be brighter than Bulb 1.
iii. Bulbs 1 and 2 have roughly the same brightness.
b. Make the circuit. What do you see? Record your observations.
c. Can you explain your observations? Do they match your prediction?
d. From your observation, what can you say about the current felt in Bulb 1 vs current in Bulb 2? (To feel smug again, test your deduction with a multimeter).
e. Draw an alternative circuit diagram that depicts the same circuit.
f. How do your observations from 6 compare to those from 5?

7. Consider the circuit diagram with three bulbs depicted on the right. Which bulbs are in parallel? Which bulbs are in series?
a. Which inequality will best describe the relative brightness of Bulbs 1,2 and 3?
i. 1>2>3
ii. 1 < 2 < 3
iii. 1 > 2 = 3
iv. 1 < 2 = 3
v. 1 = 2 = 3
b. Make the circuit. What do you see? Record your observations.
c. Can you explain your observations? Do they match your prediction?
d. From your observation, what can you say about the current felt in Bulb 1 vs current in Bulb 2? (To feel smug yet again, test your deduction with a multimeter).
e. Draw an alternative circuit diagram that depicts the same circuit.