Electricity Cost and Power Concepts

Mr. Woodward explains the concept of power as the rate at which energy is used by electrical devices, measured in watts. He introduces Joule's Law, which relates power to current and voltage, and provides an example calculation. The video also covers the cost of electricity, explaining how it is measured in kilowatt-hours and the associated costs in the Bay Area. Finally, Mr. Woodward demonstrates how to calculate the cost of running appliances, using examples of a microwave and a light bulb.

What is the definition of power in the context of electrical devices?

• The total energy used by a device

• The rate at which energy is used by a device

• The current flowing through a device

• The voltage supplied to a device

According to Joule's Law, how is power related to current and voltage?

• Power is the sum of current and voltage

• Power is the difference between current and voltage

• Power is the product of current and voltage

• Power is the ratio of current to voltage

In the example of the 60-watt light bulb, what is the calculated current when plugged into a 120-volt outlet?

• 2.0 amps

• 1.0 amps

• 0.5 amps

• 0.25 amps

What unit is commonly used in the United States to measure energy consumption on electricity bills?

• Joules

• Amperes

• Kilowatt-hours

• Watts

How much does one kilowatt-hour of electricity cost in San Francisco compared to the national average?

• 22 cents in San Francisco, 13 cents nationally

• 13 cents in San Francisco, 22 cents nationally

• 22 cents nationally, 13 cents in San Francisco

• Both are 22 cents

What is the formula to calculate the cost of running an appliance?

• Cost = Power + Time + Rate

• Cost = Power x Time x Rate

• Cost = Power / Time / Rate

• Cost = Power - Time - Rate

In the cost calculation formula, what does 'rate' refer to?

• The speed of energy consumption

• The cost per kilowatt-hour charged by the electric company

• The time the appliance is used

• The total energy used by the appliance

How much does it cost to use a typical microwave for five minutes?

• 15 cents

• 10 cents

• 5 cents

• 1.5 cents

What is the cost of running a 60-watt light bulb for five days?

• $0.58

• $1.58

• $2.58

• $3.58

Why is it important to turn off appliances when not in use?

• To increase the voltage supply

• To reduce the current flow

• To prevent power surges

• To save money on electricity bills