P1-Chapter 2 Using Energy Flashcards
Where does the chemical energy stored in your muscles come from?
From the food that you eat
Kinetic energy
Energy of a moving object due to its motion; kinetic energy (in joules, j) = 1/2 X mass (in kilograms, kg) X (speed)2 (in m2/s2)
Electrical energy
Energy transferred by the movement of electrical charge
Gravitational potential energy
Energy of an object due to its position in a gravitational field. Near the earths surface, change of GPE (in joules,j) =weight (in newtons,N) X vertical distance moved (in metres, m)
Elastic potential energy
Energy stored in an elastic object when work is done to change its shape
Chemical energy
Energy of an object due to chemical reactions in it
What energy transfers take place when you turn on a torch?
Chemical to electrical to light and transfer by heating
In terms of energy, what happens when you burn a fuel?
Chemical energy in the fuel is transferred to the surroundings, which get warmer
Conservation of energy
Energy cannot be created or destroyed
What happens to the wasted energy from a light bulb?
It is transferred to the surroundings which get warmer
Why should we talk about energy being ‘wasted’ not energy being ‘lost’?
Because the law of conservation tells us that energy cannot be destroyed
What is the equation to calculate efficiency of any appliance that transfers energy?
Efficiency= useful energy transferred by the appliance divided by total energy supplies to the appliance (x100)
In a lightbulb, for every 25 Joules of energy that are supplied to the bulb, 5 joules are usually transferred into light energy. What is the efficiency of the bulb?
The efficiency is 0.2 or 20%
A machine is adjusted so that it wastes less energy because of friction. What happens to the efficiency of the machine?
The efficiency increases
Efficiency
Useful energy transferred by a device divided by total energy supplies to the device
