Physics - Pressure, Work, Energy, Power, Efficiency Calculation

A kettle uses 100J of electrical energy to produce 7J of sound energy and 93J of thermal energy. How efficient is the kettle?

• 100%

• 7%

• 93%

• 95%

A washing machine uses 250J of electrical energy to produce 125J of useful energy. How efficient is it?

• 5%

• 50%

• 55%

• 100%

Tags

NGSS.MS-PS3-5

A hairdryer uses 300J of energy to produce 60J of sound energy and 240J of thermal energy. Calculate it's efficiency.

• 80%

• 90%

• 20%

• 100%

Tags

NGSS.MS-PS3-5

NGSS.MS-PS3-3

An iPhone charger coverts 75J of electricty in to 50J of charge and 25J of thermal energy. How efficient is the charger?

• 10%

• 100%

• 33%

• 67%

Tags

NGSS.HS-PS3-3

Which of these equations is correct?

A microwave has an efficiency of 80% and a useful power output of 663 W. The total power input to the microwave oven is ____ watts.

• 829 W

• 779 W

• 947 W

• 837 W

A solar cell used to charge a mobile phone produces 9 J of energy each second. The solar cell has an efficiency of 0.27. The total input energy to the solar cell each second is ____ J.

• 33 J

• 25 J

• 41J

• 37 J

A television converts 2.1 kJ of input energy into useful output energy at an efficiency of 70%. The useful output energy of the television is _____ joules.

• 1.5 kJ

• 1.2 kJ

• 1.8 kJ

• 2.0 kJ

A power station burns 48 kJ of energy to generate electricity. The efficiency of the power station is 0.23. The energy output of the power station is _____ kilojoules.

• 11 kJ

• 15 kJ

• 9 kJ

• 20 kJ

Which equation is correctly arranged to calculate useful power output?

• equation A

• equation B

• equation C