Lesson 21.4: Generators supply electrical energy

Lesson Focus

Explore how power plants generate the electrical energy we use daily. You will learn how electric power is measured and how to calculate your own energy consumption.

Learning Objectives

• Discover how power plants use generators to produce electrical energy.
• Describe how electric power is measured using units like watts and kilowatts.
• Calculate energy usage by multiplying an appliance's power consumption by the time it is used.
• Model your own electrical energy usage in a hands-on activity.

Power plants create electricity by converting motion.

A source like falling water or steam spins a turbine.

This rotation turns electromagnets inside a wire coil within a generator, transforming kinetic energy into electrical energy.

Electric power is the rate an appliance converts electrical energy into other forms like light or heat, measured in watts (W).

A 100W bulb is brighter because it converts energy faster than a 60W bulb.

We can calculate this rate with the formula P = V × I.

To find the total energy an appliance consumes, you need its power rating and how long it was on.

We use the formula E = P × t (Energy = Power × time).

For example, a 3kW dryer running for 30 minutes (0.5 hours) uses 1.5 kilowatt-hours of energy.

Power companies bill you for total energy used, not just the rate of use.

The standard unit for this is the kilowatt-hour (kWh)—equal to 1,000 watts of power used for one hour.

An electric meter on your home tracks total kWh usage, allowing the company to calculate your monthly bill.

Appliances are rated in watts to show their maximum power consumption.

A hair dryer (~1200W) uses much more power than a radio (~20W).

To save energy and money, focus on reducing the usage time of high-wattage items like air conditioners. Check an appliance's label to know its power demand.