Energy Stores
This energy store increases as an object increases in temperature
Thermal Store
What is the unit of measurement of Energy?
Energy is measured in Joules (J)
What is the unit of Power?
Power is measured in Watts (W)
What colour is the best at absorbing and emitting radiation?
Black
The equation for increase in thermal energy
E = m x c x ΔT
If an object is falling, this energy store is decreasing
Gravitational Store
What is the equation for work done?
Work = Force * Distance
What is the equation for Power?
P = E/t
Why would you want to wear white clothes in the sun?
White surfaces are best at reflecting radiation
What is Specific Heat Capacity?
A measure of how much thermal energy is needed to increase the temperature of a material
What is the law of conservation of energy
Energy cannot be created or destroyed, only transferred
A 4kg box is put on a 2m high bookshelf. How much gravitational energy has it gained?
E = mgh = 4 x 9.8 x 2
78.4J
What do you need to know to work out an appliance's efficiency?
Useful power output and Total power input
What will happen if you leave a black car and a white car out in the sun?
The black car will be hotter
5kg object with Specific Heat Capacity of 500J/kgoC went from 23oC to 53oC. How much energy was used?
E = mcT = 5 x 500 x (53-23)
75,000J
The name given to the store of energy within atoms
Nuclear Store
20kg object falling at 15m/s. What is the Kinetic Energy?
KE = 1/2mv2 = 1/2 x 20 x 152
2250J
What energy store is considered "wasted" or not useful energy?
Thermal Store
Name an insulating feature in a home
Floor/Wall/Foam insulating. Double glazed windows. Reflective foil behind radiators
What are the units of measurement of Specific Heat Capacity
J/kgoC
How would you work out the Kinetic Energy of an object?
KE = 1/2 x m x v2
What is work done when 500N are used to push a 5kg box 15m
Work done = F x s = 500 x 15
7500J
30W Light bulb used for 10 minutes vs 700W Microwave used for 30s. What is the difference in energy used?
30 x 600 = 18000J. 700 x 30 = 21000J
Difference = 3000J
What is a Perfect Black Body?
An object that absorbs and emits all radiation
On a graph of Temperature against Thermal Energy, how do you work out Specific Heat Capacity
1/gradient