Energy stores and systems

A system is an object or a group of objects

A closed system is one where no energy can enter or escape from the surroundings. The total energy in a system never changes.

Kinetic energy - Energy an object has when its moving

Elastic energy - energy an object has when its stretched or compressed

Gravitational potential enegry - Energy an object has because of its height above the ground

Magnetic energy - energy a magnetic object has when near a magnet or in a magnetic field

Thermal energy - energy a object has when its heated

Chemical energy - energy that can be transferred in chemical reactions involving food, fuels and batteries

Nucleur - energy stored in the nucleus of the atom

electrostatic - energy a charged object has when near another charged object

Energy transfers -

• Radiation

• Mechanical

• heating

• electricity

  kinetic energy =0.5 ×mass ×(speed)2

[Ek = 12 m v2]

elastic potential energy =0.5 ×spring constant ×(extension)2

[Ee  = 12 k e2]

g.p.e. =mass ×gravitational field strength ×height

[  Ep =m g h⁢ ]

Specific heat capacity

Specific heat capacity is the amount of energy required to raise the temperature of 1kg of a substance by 1 degrees.

Required practical one :

Required practical one : : investigation to determine the specific heat capacity of one or more materials. The investigation will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored.

• place a beaker on a balance and press 0

• Now place your substance in the beaker to measure its mass

• Place a thermometer and immersion heater into the substance allowing you to read the starting temperature of the substance

• Wrap insulating foam around the beaker to stop the thermal energy transfer to the surroundings

• connect a joulemeter to the immersion heater. Telling you how many joules of electrical energy passes into the immersion heater

• Now time for 30mins allowing the temperature to rise enough for you to accurately to read off the thermometer

• Read the total number of joules that passed into the immersion heater and the final temp.

• You now use all of this info to calculate the SHC of the substance.

Safety precautions -

• Dont handle block whilst heating

• keep block on a heatproof mat

Power

Power is defined as how much work is done per second

power = energy transferred/ time

[P = Et]

1 watt = 1 joule of energy transferred per second