P1+2 Energy Flashcards
What are the energy pathways?
Heating, radiation, mechanical, electrical
What are the energy stores?
Chemical, thermal, kinetic, elastic, gravitational, electrostatic, nuclear
What is conservation of energy?
Energy can’t be created or destroyed, this applies to all energy changes.
What is a closed system?
A system in which no energy transfers take place out of or into the energy stores of the system.
Work done equation
work done, W(j) = force applied, F(n) x distance travelled, d(m)
What does energy transferred equal?
Work done.
Gravitational potential energy equation
GPE(j) = mass, m(kg) x gravitational field strength, g(N/Kg) x height, h(m)
Kinetic energy equation
1/2 x mass, m(kg) x speed^2, v^2 (m/s^2)
Elastic potential energy equation
1/2 x spring constant, K(N/m) x extension^2, e^2(m^2)
What is Useful energy?
Energy transferred to where it is wanted in the way it is wanted.
What is Wasted energy?
Energy that is not usefully transferred.
What happens to energy as it dissipates (spreads out)
It becomes less and less useful
Equation for efficiency
efficiency=useful output energy transferred by the device(j)/total input energy supplied to the device(j)
Equation for power
power, p(w) = energy transferred to appliance, e(j)/time taken for energy to be transferred, t(s)
Equation for specific heat capacity
Change in energy, ∆E(j) = mass, m(kg) x specific heat capacity, c(j/kg) x temperature change, ∆θ(°C)
What does the specific heat capacity of a substance mean?
The energy needed to change 1Kg of a substance by 1°C
What are examples of electrical appliances and why are they used?
They could be heating, lighting and producing sound. They can transfer energy quickly and efficiently so they do not waste energy.
What actually is power?
The energy you supply per second is the power.
How to calculate power wasted?
power wasted = total power in - useful power out
What are the best conductors of energy?
Metals
What is thermal conductivity?
Thermal conductivity is the rate at which energy is transferred through something by conduction.
What does insulation do to energy transfer?
The thicker the layer of insulating material, the lower the rate of energy transferring through.
What is infrared radiation?
It is part of the electromagnetic spectrum and is given out by the sun. All objects emit and absorb infrared radiation. It also increases the amount emitted with the heat.
What is black body radiation?
It is the radiation emitted by a perfect black body. It absorbs all the radiation incident on it.
