Lesson 3 – T: Transform Your Learning: Measuring Power & Energy
T: Transform Your Learning
Show What You Can Do and Connect It Forward
Engineers often change one part of a design, test what happens, and compare the results. You could change the resistor value, add another LED, or compare different loads. By doing this, is becomes clearer how the change affects current, power, and energy use.
When resistance or load changes, current can change. When current changes, power also changes because power depends on both voltage and current. This is why engineers measure instead of guessing, and use their measurements to make design decisions.
Look at this modification chart showing the changes between an original and modified circuit.
|
Circuit |
What Changed |
Measured Voltage (V) |
Measured Current (A) |
Calculated Power (W) |
|---|---|---|---|---|
|
Original circuit |
Starting setup: one red LED and a 220 Ω resistor in series with a 3 V battery pack |
3.00 |
0.0050 |
0.0150 |
|
Modified circuit |
Replaced the 220 Ω resistor with a 1,000 Ω resistor; kept the same LED and battery pack |
3.00 |
0.0012 |
0.0036 |
Explain With Evidence
How did the modification change power? Use measurements as evidence.
Connect to Engineering
How does this connect to real energy systems?
Engineering Insight
Changing resistance or load changes current, and that change affects power. Engineers measure these values to make design decisions instead of relying on assumptions.
Check Your Understanding
- Why do engineers measure power instead of just voltage? Use evidence.
- What happens to power when current changes?
- Looking Ahead: How can measuring voltage and current help engineers design a useful solar mini-grid?
Closure: Connecting Lesson 3 to Lesson 4
In Lesson 3, you measured voltage and current in a battery-powered LED circuit and used those measurements to calculate power and energy. You also saw that changing part of a circuit can change its current and power, so engineers use measurement evidence rather than guessing.
In Lesson 4, you will take the next step by building and testing a circuit of your own. You will add resistance to your measurements, use Ohm’s Law to examine the relationship among voltage, current, and resistance, and use those ideas to make purposeful circuit-design decisions.