Introduction to Physical Science: Power

The lecture introduces the concept of power as the rate at which work is done, measured in watts. It explains how power is calculated using the example of a woman running up stairs, combining kinetic and potential energy. The discussion extends to power efficiency, highlighting energy loss in systems like coal power plants. Various examples of power levels, from pocket calculators to supernovae, are compared. The lecture concludes with a practical example of calculating energy consumption and cost for a computer, emphasizing the importance of understanding power in everyday applications.

What is the scientific definition of power?

• The amount of work done

• The time taken to do work

• The rate at which work is done

• The energy required to do work

If you lift an object slowly, how does it affect the power used?

• Increases the power

• Does not affect the power

• Decreases the power

• Doubles the power

In the example of the woman running up the stairs, what two types of energy are considered?

• Potential and thermal energy

• Electrical and kinetic energy

• Thermal and kinetic energy

• Kinetic and potential energy

What is the unit of power?

• Pascal

• Watt

• Newton

• Joule

How much power is required for a woman to run up a three-meter flight of stairs in 3.5 seconds?

• 1000 watts

• 750 watts

• 250 watts

• 538 watts

What is the efficiency of a coal power plant that consumes 2500 megawatts to produce 1000 megawatts of electricity?

• 40%

• 50%

• 60%

• Less than 50%

Which of the following has the highest power rating?

• Pocket calculator

• Lightning bolt

• Clothes dryer

• Aircraft carrier

How is energy use expressed on an electric bill?

• In joules

• In watts

• In kilowatt hours

• In kilowatts

If a computer consumes 0.2 kilowatts and runs for 6 hours per day, how much energy does it use in a month?

• 12 kilowatt hours

• 24 kilowatt hours

• 30 kilowatt hours

• 36 kilowatt hours

What is one key point about energy conversion to power?

• It always involves thermal energy

• It is always 100% efficient

• It is never 100% efficient

• It does not involve energy loss