Y9 PHYSICS HWK LC2 #4 - Power

What is the equation for power?

• Ep = m x h x g

• Ek= ½ x m x v²

• Ee = ½ x k x e²

• P = E / t

P = E / t.

What is does the symbol t mean?

• power

• energy

• temperature

• time

Watts are a unit of .....

• power

• energy

• time

• mass

• extension

Calculate the power of a device that transfers 500J of energy in 300s

P = E / t

• 0.6J

• 0.6W

• 1.7J

• 1.7W

Calculate the power of a device that transfers 1790J of energy in 226s

P = E / t

• 0.13J

• 0.13W

• 7.9J

• 7.9W

Calculate the energy transferred in a device that is turned on for 60s that has a power rating of 100W

P = E / t

• 1.7J

• 0.6J

• 6000W

• 6000J

Calculate the energy transferred in a device that is turned on for 2000s that has a power rating of 250W

P = E / t

• 500,000J

• 8J

• 0.125W

• 0.125J

Select the correct calculations: (2 marks)

P =

• I x V

• I / V

• V / I

• I² x R

• R² x I

A hairdryer uses a current of 10A and has a voltage of 3V. How much power does it use?

• 30W

• 30w

• 0.3 W

• 3.3W

What is 80% of 2400 watts?

• 1920 watts
• 19,200 watts
• 2000 watts
• 20,000 watts