End Of Unit Questions Flashcards
What form of energy does a stretched spring have?
Elastic potential energy
When is electrical energy transferred?
When an electrical current flows through it
What are the useful energy transfers that take place in a hairdryer?
Electrical energy to kinetic energy and energy transferred by heating
What are the useful energy transfers that take place in a TV?
Electrical energy to light and sound
What energy transfers take place when you lift a ball into the air and then drop it so it falls to the ground?
Kinetic energy to gravitational potential energy to kinetic energy
Wear and tear causes a particular machine to waste more energy. What happens to the efficiency of this machine?
It’s efficiency decreases
In an electrical motor, 250J are transferred to the surroundings by heating for every 1000J of electrical energy supplied. What is the efficiency of the motor as a fraction?
3/4
Why is an electrical heater the only appliance that may have the efficiency of 100%?
Because it is designed to transfers energy by heating, which is normally how other machines waste energy
Why do electrical appliances such as TVs and computers have vents?
So that wasted energy can be transferred easily to the surroundings making them warmer, rather than the TV or the computer
60J of energy are supplied each second to a light bulb, the bulb transfers 18J of energy to light each second. How much energy does the bulb waste each second?
42J
When a kettle full of cold water is brought to boiling point, 720,000J of energy are transferred to the water. If the kettle has an efficiency of 96%, how much energy is supplied to the kettle to boil the water?
750,000J
What form of energy does a moving car have?
Kinetic energy
