Option 1

Heat a fixed volume of water until the temperature has increased by an amount of your choice.

Option 2

Heat a fixed volume of water for a time of your choosing.

In each case you must measure and record:

- the volume of water - the current used by the bulb - the voltage provided by the powerpack - the temperature rise of the water - the time taken

1. Calculate the power of the bulb 2. Calculate the energy used by the bulb 3. Calculate the heat energy that went into the water 4. Calculate the light energy produced by the bulb 5. Draw a Sankey diagram to show the energy change that took place in the bulb 6. Calculate the efficiency

1. Calculate the power of the bulb Use

Power = Voltage × Current

2. Calculate the energy used by the bulb Use

Energy = Power × time

3. Calculate the heat energy that went into the water Use

Energy = mass × specific heat cap. × temp rise

4. Calculate the light energy produced by the bulb Use

light energy = total energy in – wasted heat energy

5. Draw a Sankey diagram to show the energy change that took place in the bulb

Show the energy in and out using scaled arrows

6. Calculate the efficiency

Use the efficiency equation you learned last lesson