P1 - conservation and dissipation of energy Flashcards
explain each energy store
chemical includes fuels, food, chemicals found in batteries
kinetic - the energy an object has when it’s moving
gravitational potential - the energy stored in an object because of its position
elastic potential - the energy stored in a springy object when it’s stretched or squashed
thermal energy - the energy a substance has because of it’s temperature
draw a flow diagram of the energy transfers in a torch lamp
chemical energy store in battery -> electric current in wires -> energy transferred to surroundings -> light waves AND increase in thermal energy store of surroundings
define a closed system
a system that experienced no net change in its total energy when energy transfers occur within it
what is the law of conservation of energy
energy cannot be created or destroyed
what is the equation for work done
work done W (joules) = force applied F (newtons) x distance moved along the line of action if the forces S (meters)
where is work done to overcome friction transferred to? (in terms of energy stores)
to the thermal stores of the objects that rub together
what is the equation for the change in gravitational potential energy
gravitational potential (joules) = weight (newtons) x change in height (meters)
what is the equation for kinetic energy
kinetic energy = 1/2 x mass x speed^2
what is hookes law
force = spring constant x extension
what is useful energy
energy transferred to where it is saved in the way that it is wanted
what is wasted energy
energy that is not usefully transferred
what happens to the rest of energy that is not usefully transferred
it is dissipated and stored in less useful ways
how does friction affect energy?
it causes energy to be wasted as energy is being transferred to the thermal store
what happens to wasted energy eventually
it gets transferred to the surroundings (they become warmer)
what happens as energy dissipates
it gets less and less useful
what is the equation for efficiency
efficiency = (useful energy output/total energy input)x100
how do you reduce friction
lubricate moving parts
how do you reduce wasted energy in a circuit as a result of resistance
use wires with as little electrical resistance as possible
how do you reduce air resistance
streamline the shapes of moving objects
how do you reduce wasted sound energy
cut out noise (tighten loose parts to reduce vibration)
why do clockwork radios need to be wound up
windup the clockwork spring in it, increasing elastic potential energy of spring, when spring unwinds energy from elastic potential energy store is transferred to kinetic store and turns a small electric generator in the radio
what happens to an appliances energy transfer if it gets more powerful
it transfers energy faster
what is the equation for wasted power
power wasted = total power in - useful power out
