energy

• energy is measured in joules (j)
• 1 kJ = 1000 J
• lots of types of energy
• magnetic energy - pull of a magnet
• gravitational potential - height of object
• electrostatic energy - between charged objects
• kinetic energy - anything moving
• thermal energy - anything hot
• chemical energy - match, battery, fuels
• nuclear energy - nuclear bomb, nuclear power station
• elastic potential energy - stretched string, elastic
• energy cannot be created or destroyed (law of conservation of energy)
• ways to transfer energy - electrical, work done, heat, radiation (sound or light)
• heat will flow from high to low - in temperature
• thermal equilibrium - heat will flow until the temperature is equal everywhere
• conduction - solid objects are heated and the particles vibrate with kinetic energy, particles then transfer the energy along
• rate of thermal conductivity = thickness of material, temperature difference across material, thermal conductivity of material
• thermal radiation is emitted by all objects
• hotter objects emit more radiation than colder ones
• thermal radiation can be absorbed, reflected or transmitted
• non renewable energy is when sources of energy come from dead plants or fossils so they cannot be replaced once used
• renewable energy is when the source comes from the environment
• power is how much energy transferred per second
• e = p x t (energy = power x time)
• 7200J = 60W x 120S
• work is done on an object if the force applied moves the object along in the direction of the force
• w = f x d (work done = force x distance)
• 20Nm = 10N x 2m (work done)
• convection - fluid particles gain energy and move apart
• in convection the particles become less dense then they rise up, and in its space replaced by denser fluid