Lesson 4 – T: How Do I Build a Circuit and Calculate Power & Energy?
T: Transform Your Learning
Show what you can do and connect it forward
You started this lesson able to measure voltage and current. Now you can build a circuit, use Ohm’s Law to design it toward a target, calculate the power it uses, and turn that power into energy over time. You can also estimate a load and explain a trade-off to fit a limit — the same reasoning engineers use to size real systems.
Engineering Notebook
State Ohm’s Law and explain how you would use it to choose a resistor for a target current.
Check Your Understanding
- State Ohm’s Law and explain how you would use it to choose a resistor for a target current.
- Show how you calculated power (P = V × I) and energy (Wh) for one trial, using your own numbers.
- Why do engineers need a load estimate in watt-hours before deciding how big a power source must be?
- Describe one trade-off you would make to meet an energy need under a constraint, and what you gain by it.
Closure: Connecting Lesson 4 to Lesson 5
In Lesson 4, you built circuits, used Ohm’s Law to design them, and turned power into energy over time. You also estimated a load and made a trade-off to fit a constraint.
In Lesson 5, your power source changes from a battery to a solar cell. You will investigate how light can be transformed into electrical energy through the photovoltaic effect, and you will use the same voltage, current, power, and energy tools to explore how the amount of light reaching a solar cell affects its output — and how to size a solar system for a mini-grid.
Final Takeaway
A circuit that works is not automatically a good design. Engineers measure voltage, current, and resistance, calculate power and energy, and weigh trade-offs so they can build systems that meet a real energy need.