Electric Power and Energy — Reading Comprehension

Electric power is a measure of how quickly electrical energy is used or transferred. Every time a light turns on or a computer runs, energy is being used at a certain rate. Understanding power helps us make smart choices about the devices we use and how much energy we consume. This passage explains how electric power is calculated, how it is measured in watts, and how we keep track of our energy use with kilowatt-hours. It also compares the power ratings of common devices and explores ways to use energy more efficiently.

How Electric Power Works

The amount of power a device uses depends on two main factors: voltage (the push that moves electric charges) and current (the flow of electric charges). The basic formula for electric power is P = V × I, where P is power in watts, V is voltage in volts, and I is current in amperes. For example, if a device operates at 120 volts and draws 2 amperes of current, it uses 240 watts of power (120 × 2 = 240). The higher the power, the more energy is consumed per second. This is why a microwave (1000W) uses much more energy than an LED bulb (10W) when both run for the same amount of time.

Measuring and Paying for Energy

Energy companies bill customers based on the amount of energy they use, not just the power rating of each device. The standard unit for energy use is the kilowatt-hour (kWh), which equals 1,000 watts used for one hour. To find out how much energy a device uses, multiply its power (in kilowatts) by the number of hours it runs. For example, a hair dryer rated at 1500W (or 1.5kW) used for 2 hours uses 3 kWh (1.5 × 2 = 3). If a household pays $0.15 per kWh, running the hair dryer for 2 hours would cost $0.45. By comparing the energy used by different devices, people can make decisions to lower their bills and reduce their environmental impact.

Comparing Devices and Saving Energy

Different devices have different power ratings. An LED bulb uses about 10W, a laptop around 50W, a microwave about 1000W, and a hair dryer up to 1500W. Using energy-efficient devices, such as LED bulbs, can significantly reduce energy use over time. Conservation tips include turning off devices when not in use, unplugging chargers, and choosing appliances with high energy efficiency ratings. These actions help conserve resources, reduce pollution from power plants, and save money. Choosing efficient devices and using them wisely is good for both the planet and your wallet.

Understanding electric power and energy use helps us see the connections between science, technology, and our daily lives. By learning how to calculate power and energy, we can make better choices for ourselves and our communities.

Interesting Fact:
Some LED bulbs can last over 20 years, using about 80% less energy than old incandescent bulbs!

What does electric power measure?

Which formula is used to calculate electric power?

What unit is used to measure electric power?

What does 'kilowatt-hour' mean?

According to the passage, which uses the most power?

What is one way to save energy at home?

What is the main purpose of comparing device power ratings?

True or False: Using energy-efficient devices can lower your electricity bill.

True or False: Energy companies bill customers by the size of their appliances.

Which of the following is an example of energy efficiency?