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kinetic and potential energy stores & specific heat capacity &…
kinetic and potential energy stores & specific heat capacity & investigating specific heat capacity
movement means energy in a objects kinetic energy store
2) the energy in the kinetic energy store depends on the objects mass and speed the greater its mass and the faster its going the more energy there will be in its kinetic energy store
3) Ek= 1/2mv squared
1) anything that is MOVING has energy in its KINETIC ENERGY STORE energy is transferred to this store when an object speed up and is transferred away from this store when a object slows down
raised objects store energy in gravitational potential energy stores
2) the amount of energy in a gravitational potential energy store depends on the objects mass its height and the strength of the gravitational field the object is in
3) us this equation to find the change in energy in a objects gravitational potential energy store for a change in height h
1) lifting a object in a gravitational field requires work causing a transfer of energy to the gravitational potential energy store of the raised object the higher the object is lifted the more energy is transferred to this source
Ep = mgh
stretching can transfer energy to elastic potential energy stores
stretching or squashing an object transferred energy to its elastic potential energy store as the limit of proportionality has not been exceeded energy in the elastic potential energy store of a stretched spring can be found using
Ee= 1/2 ke 2 squared
different materials have different specific heat capacity
3) materials that need to gain lots of energy in their thermal energy stores to warm up also transfer loads of energy when they cool down again they cant store a lot of energy
4) the measure of how much energy a substance can store is called specific heat capacity
2) eg you need 4200 j to warm 1 kg of water by 1.c but only 139 j to warm 1 kg of mercury by 1.c
SPECIFIC HEAT CAPACITY IS THE AMOUNT OF ENERGY NEEDED TO RAISE THE TEMERATURE OF 1KG OF A SUBSTANCE BY1.C
1) more energy needs to be transferred to the thermal energy store of some materials to increase their temperature than others
^E = mc^ 0
^=change in thermal energy (j) m=mass c=specific heat capacity 0=temp change
practical for specific heat capacity
3) measure the initial temperature of the bloc and set the potential difference (voltage ) of the power supply to 10v turn on the power supply and the stop watch
4) when you turn on the power the current in the circuit (i.e. the moving charges) does work on the heater transferring energy electrically from the power supply to the heaters thermal energy store this energy store this energy is then transferred to the materials thermal energy store by heating causing the materials temp to increase
5) as the block heats up us the thermometer to measure its temp eg every minuet keep an eye on the ammeter the current through the circuit shouldt change
2) measure the mass of the block then wrap it in a insulation layer eg thick newspaper the reduce the energy transferred from the block to the surroundings insert the thermometer and heater
1) to investigate a solid material you will need a block of the material with 2 holes in it (for the heater and thermometer to go into )
6) when you collected enough readings (10) turn the power supply off
7) calculations to work out specific heat capacity
if you assume that all the energy supplied to the heater has been transferred to the block you can plot a graph of energy transferred to the thermal energy store of the block against temperature
find the gradient of the straight part of the graph this is ^0/^E so the shc of the materials of the block is 1/(GRADIENT X THE MASS OF THE BLOCK )
using sing your measurements of the current and the potential difference of the power supply you can calculate the power supplied to the heater using P=VI you can use this to see how much energy E has been transferred to the heater at the time of each temperature reading using the formula E=Pt where t is the time in seconds since the experiment began
8) repeat experiment with different materials and compare shc