Best examples of investigating energy loss in electrical circuits in the lab and classroom

Lab-friendly examples of investigating energy loss in electrical circuits

When students ask where the energy “goes” in a circuit, you don’t win them over with theory alone. You win them with experiments. Some of the best examples of investigating energy loss in electrical circuits are also the simplest to build:

• A resistor that gets hot while the battery voltage sags.
• A phone charger that draws power even when nothing is plugged in.
• A dim incandescent bulb next to a bright LED using the same electrical power.

These are the kinds of real examples that turn the abstract idea of energy conservation into something you can feel, measure, and argue about.

Classic example of energy loss: heating in resistors and wires

A straightforward example of investigating energy loss in electrical circuits is to measure how electrical energy turns into thermal energy in a resistor or a long wire.

You can set this up with a DC power supply, an adjustable resistor (or several fixed resistors), an ammeter, a voltmeter, and a thermometer or temperature probe. Students measure voltage across the resistor and current through it, then calculate power using \(P = VI\). That electrical power becomes heat, which raises the resistor’s temperature.

The investigation gets interesting when you:

• Compare short, thick wires to long, thin wires at the same current, and track how much they heat.
• Keep the same voltage but change resistance and see how power — and heating — respond.
• Plot temperature rise versus time and compare it to calculated electrical energy input \(E = P t\).

This is one of the clearest examples of investigating energy loss in electrical circuits because students can literally feel the resistor warming up. The “lost” energy is right there as thermal energy, not missing at all.

For teachers who want to go deeper, the U.S. Department of Energy has accessible background material on resistive heating and power loss in transmission lines: https://www.energy.gov

Lighting comparison: incandescent vs LED as real examples

Lighting is where students already have opinions, so it’s perfect territory for real examples of investigating energy loss in electrical circuits.

Set up two separate circuits:

• Circuit A: A traditional incandescent bulb.
• Circuit B: An LED bulb or LED strip light designed for the same supply voltage.

Measure the current and voltage for each circuit, calculate power, and then compare brightness and temperature. With an infrared thermometer or simple touch (safely, and only once power is off or with proper guards), students notice the incandescent bulb gets very hot, while the LED stays relatively cool.

Both bulbs convert electrical energy into light and heat, but in very different proportions. The incandescent “wastes” a large fraction as heat; the LED converts a larger fraction into visible light. This contrast is one of the best examples of investigating energy loss in electrical circuits because students already see the consequences at home in the form of energy bills and bulb lifetimes.

For more background on lighting efficiency and energy use trends in the U.S., the Energy Information Administration (EIA) provides up‑to‑date data and charts: https://www.eia.gov

Power supply and phone charger inefficiency: modern 2024–2025 context

If you want examples of investigating energy loss in electrical circuits that feel current, plug in a modern phone charger or laptop brick. Almost every student owns one.

There are two main investigations here:

1. Vampire power (standby losses)

Connect a phone charger to a power strip with a plug‑in energy meter. Measure power draw with no phone connected, then with a phone charging, then with a phone fully charged but still plugged in.

• The idle draw with no device connected is a direct example of energy loss: electrical power is being consumed, mostly turning into heat inside the charger’s electronics.
• The difference between “charging” and “fully charged but still plugged in” shows how much extra energy is being used just to sit there.

Students can extrapolate: one charger might waste only a fraction of a watt, but multiply that by millions of chargers plugged in 24/7 and the energy adds up. This gives a modern, data‑driven example of investigating energy loss in electrical circuits that connects directly to real‑world behavior.

2. Efficiency curves of switching power supplies

More advanced classes can measure input power at the wall and output power on the USB side at different loads. Plotting efficiency (output power divided by input power) versus load reveals that chargers and laptop bricks are most efficient near their rated load and less efficient at very low or very high loads.

In 2024–2025, many manufacturers publish efficiency ratings that meet or exceed ENERGY STAR or similar international standards, but the lab data shows that “high efficiency” is not a single number — it’s a curve. This experiment becomes one of the more nuanced examples of investigating energy loss in electrical circuits, because it forces students to think about how design and operating conditions affect real performance.

For reference on appliance and electronics efficiency standards, see the U.S. Department of Energy’s appliance standards pages: https://www.energy.gov/eere/buildings/appliance-and-equipment-standards-program

Motor and fan experiments: electrical to mechanical to heat

Motors are another rich source of examples of investigating energy loss in electrical circuits because they involve multiple energy transformations.

Take a small DC motor or a PC cooling fan. Measure the electrical power going in by recording voltage and current. Then explore what happens under different mechanical loads:

• No load: the motor spins freely. Most of the input power is lost as heat in the windings and bearings, plus a bit as sound.
• Moderate load: attach a small fan blade, pulley, or friction brake. Some electrical energy becomes mechanical work (moving air or lifting a small weight), but losses also rise.
• Heavy load or stall: the motor draws a large current, heats quickly, and almost all the electrical energy becomes heat.

Students can compare input electrical energy to useful mechanical output, estimated from force and speed measurements. The gap between the two — the inefficiency — is a very tangible example of investigating energy loss in electrical circuits in a context that feels practical, from household fans to electric vehicles.

Long-wire and transmission-style experiments

Full‑scale power transmission lines are out of reach for most classrooms, but the underlying physics is not. A bench‑top long‑wire experiment provides one of the more realistic examples of investigating energy loss in electrical circuits.

Use a long coil of thin wire as a model “transmission line” feeding a resistive load at the far end. Measure the voltage and current at the source and at the load. Students will see:

• The current is the same everywhere in a simple series circuit.
• The voltage at the load is lower than at the source because some energy is lost as heat in the wire’s resistance.

By calculating power at the source and power at the load, students can estimate the fraction of energy lost in transmission. Then you can connect this to real grid data, where utilities report line losses on the order of a few percent. This gives a scaled‑down but realistic example of investigating energy loss in electrical circuits that mirrors what utilities worry about every day.

The U.S. Energy Information Administration provides data and discussion on transmission and distribution losses: https://www.eia.gov/tools/faqs/faq.php?id=105&t=3

LED drivers, EV chargers, and other 2024–2025 case studies

To bring the topic into the 2024–2025 landscape, it’s worth looking at how modern devices manage energy loss.

LED driver circuits

Modern LED bulbs and fixtures contain driver circuits that convert AC mains power to the low‑voltage DC current LEDs need. These drivers are not perfect. They lose some energy as heat in switching transistors, diodes, and inductors.

In the lab, students can:

• Measure the AC power drawn by an LED bulb at the wall.
• Estimate the optical power output using manufacturer data (lumens per watt) and published conversion factors.
• Infer how much of the input energy is lost in the driver and as heat in the LEDs themselves.

This makes LED lighting not just a “good vs bad” comparison with incandescent bulbs, but a nuanced example of investigating energy loss in electrical circuits inside modern electronics.

Electric vehicle (EV) charging

EV charging is another timely case. While you won’t be tearing down a full EV in class, you can model the concepts using a battery pack and a DC power supply.

Students can measure:

• Electrical energy delivered by the charger (voltage × current × time).
• Change in stored energy in the battery, using battery capacity estimates and voltage curves.

The difference includes energy lost as heat in charger electronics, cables, and the battery’s internal resistance. Public data from EV manufacturers and independent labs often quote overall charging efficiencies in the 85–95% range, depending on power level and temperature. That gap between the wall and the battery is a large‑scale, real‑world example of investigating energy loss in electrical circuits that connects directly to climate and energy policy discussions.

Data handling and error analysis in energy loss experiments

All of these examples of investigating energy loss in electrical circuits are only as good as the measurements behind them. A few habits make the investigations more credible:

• Record voltage and current with stated uncertainties, not just single numbers.
• Take multiple readings at each setting and average them.
• Track temperature, especially in resistor and motor experiments, because resistance can change with heating.
• Compare experimental energy balances to theoretical expectations from \(P = I^2 R\), \(P = VI\), and \(E = P t\).

Encouraging students to estimate percent differences between input and output energy, and to discuss where the “missing” energy went, turns these setups from simple demonstrations into real investigations.

For teachers building lab curricula, physics education research groups at universities often publish open‑access lab modules and error‑analysis guides; for example, many U.S. physics departments host materials under .edu domains that can be adapted to local needs.

FAQ: examples of investigating energy loss in electrical circuits

Q1. What are some easy classroom examples of investigating energy loss in electrical circuits?
Simple resistor heating tests, incandescent vs LED bulb comparisons, and phone charger standby power measurements are all easy to set up with standard lab gear. These give fast, visible evidence of energy turning into heat and light.

Q2. What is a good example of energy loss in a household circuit?
A classic example of energy loss at home is an old incandescent lamp. Most of the electrical energy becomes heat instead of visible light. Another is a plugged‑in phone charger that feels warm even when it isn’t charging anything.

Q3. How do engineers reduce energy loss in electrical circuits?
They use lower‑resistance conductors, higher operating voltages for transmission, switching power supplies with better efficiency, and components like LEDs and high‑efficiency motors. Modern design standards and regulations push manufacturers to publish and improve efficiency ratings.

Q4. Are energy losses always a bad thing?
Not always. Sometimes the desired outcome is heat, as in electric heaters or toasters. The key is whether the energy form you get matches the job you want done. In most electronics, though, extra heating means wasted energy, shorter component life, and higher operating costs.

Q5. How can students extend these examples of investigating energy loss in electrical circuits at home?
They can use a plug‑in energy meter to compare old and new appliances, measure how much power different chargers draw at idle, or test how warm different types of bulbs get after a few minutes. With careful notes, these small projects become personal, real‑world examples of investigating energy loss in electrical circuits beyond the classroom.