Skip to main content

Learning Introductory Physics with Activities

Paul J. Emigh, Rebecka Tumblin, Kathryn Hadley, Danielle Skinner

Section 26.6 Circuit Loops

Start by using the Circuits PhET Simulation. You may also want to recall the behavior of an Incandescent Light Bulb.
🔗

Subsubsection Activities

🔗

Activity 26.6.1. Combinations of Light Bulbs.

Predict how bulbs A and B will change in brightness when we close the switch!
🔗
A circuit diagram with one battery. Bulb A is above bulb B, and a parallel branch with an open switch and bulb C is connected across bulb B.
Figure 26.6.1. A circuit diagram.
🔗

(a)

Identify any bulbs that are in series or in parallel. Sketch voltage diagrams for each branch in both circuits. Rank all six bulbs by brightness.
🔗
Above: A circuit diagram with one battery. Bulb A is above bulb B, and a parallel branch with an open switch and bulb C is connected across bulb B. Below: another circuit diagram with one battery. Bulb D and E are in series along one parallel branch, and bulb F is on its own along another parallel branch.
Figure 26.6.2. Two circuit diagrams.
🔗
🔗

(b)

Consider the circuits below one at a time. For each new circuit, use voltage diagrams to predict how the brightness of each bulb compares to the bulbs in the previous circuits. After you make your predictions, use the simulation to check your predictions! Modify your diagrams based on your observations, if necessary
🔗
Circuit 1: one battery and bulb 1. Circuit 2: two batteries and bulb 2. Circuit 3: two batteries in opposite orientations and bulb 3. Circuit 4: two upright batteries and one inverted battery and bulb 4. Circuit 5: an inverted battery, then bulb 5, then 3 upright batteries. Circuit 6: on the left, bulb 6 between two upright batteries; on the right, bulb 7 between two oppositely oriented batteries.
Figure 26.6.3. Six circuit diagrams.
🔗
🔗
🔗

Activity 26.6.2. Complicated Loops.

Predict whether the brightness of the light bulb will increase, decrease, or remain the same when the switch is closed.
🔗
A circuit diagram with three vertical parallel branches. The outer branches have upright batteries and the middle branch has a light bulb. A switch lies between the bulb and the right battery.
Figure 26.6.4. A circuit diagram.
🔗

(a)

Why do you think the upper circuit behaves the way it does? How does the current through each battery change?
🔗
Two circuit diagrams with three vertical parallel branches. Top: The outer branches have upright batteries and the middle branch has a light bulb; a switch lies between the bulb and the right battery. Bottom: The left branch has an upright battery, the right branch has an upright battery and a light bulb, and the middle branch has a light bulb; a switch lies between the middle and right branches.
Figure 26.6.5. Two circuit diagrams.
🔗
Predict what will happen to each light bulb in the bottom circuit when you close the switch.
🔗
Construct this circuit in the simulation and check your predictions.
🔗
If you have not already done so, draw voltage diagrams for this circuit. Make sure your diagrams agree with your observations!
🔗
🔗

(b)

When the switch is closed:
🔗
  1. Predict the relative brightness of the three light bulbs. Explain.
    🔗
    🔗
  2. Construct this circuit in the simulation and check your predictions.
    🔗
    🔗
  3. If you have not already done so, draw voltage diagrams for this circuit. Make sure your diagrams agree with your observations!
    🔗
    🔗
A circuit diagram with three vertical parallel branches. The outer branches each have an upright battery and a light bulb and the middle branch has a light bulb. A switch lies between the middle and right branches.
Figure 26.6.6. A circuit diagram.
🔗
When you open the switch:
🔗
  1. Predict how (if at all) the brightness of each light bulb will change. Explain.
    🔗
    🔗
  2. Construct this circuit in the simulation and check your predictions.
    🔗
    🔗
  3. If you have not already done so, draw voltage diagrams for this circuit. Make sure your diagrams agree with your observations!
    🔗
    🔗
Propose a modification to one of the circuits you have explored today. Make a prediction and then test it out using the simulation!
🔗
🔗
🔗
🔗
PrevTopNext