Electrical Energy Transfers: Calculating Power and Energy

The video tutorial explains three equations for calculating electrical power and demonstrates how to use them to determine energy transfer in electrical devices. It covers the equations P = E/t, P = I*V, and P = I^2*R, explaining the meaning of each symbol and the importance of using correct units. The tutorial provides three examples: a toaster, a kettle, and a hair dryer, showing step-by-step calculations of energy transfer using the given equations.

Which of the following equations is used to calculate power when energy and time are known?

• P = V / I

• P = I² × R

• P = E / t

• P = I × V

In the first example, what is the power of the toaster if it draws a current of 7 amps and has a potential difference of 230 volts?

• 1,800 watts

• 1,700 watts

• 1,500 watts

• 1,610 watts

How much energy is transferred by the toaster in 120 seconds?

• 210,000 joules

• 180,000 joules

• 200,000 joules

• 193,200 joules

What equation is used to calculate the power of the kettle in the second example?

• P = I × V

• P = E / t

• P = I² × R

• P = V / I

How much energy is transferred by the kettle in 3 minutes?

• 547,560 joules

• 500,000 joules

• 600,000 joules

• 450,000 joules

In the third example, what is the combined equation used to calculate energy transferred by the hair dryer?

• E = P × t

• E = I × V × t

• E = I² × R × t

• E = V² / R × t

How much energy is transferred by the hair dryer in 90 seconds?

• 198,000 joules

• 200,000 joules

• 180,000 joules

• 210,000 joules