|Home||Biology||Chemistry||Physics||Controlled Assessments||Long Answer Questions||11-14 Science||Big Moments in Science||Linkup|
Energy is the ability to do work.
Energy makes things happen. It makes a car move, a person talk, alight bulb shine, a cooker cook food.
Forms of energy
Potential/stored energy can be stored as:
Now try to identify the forms of nergy in each of these:
Conservation of energy
We often say that energy cannot be created nor destroyed (you can't create new energy or destroy energy). You can only change it from one form to another. This is called the Law of Conservation of Energy.
This leads us to the concept of energy transformations (transfers)
A light bulb transfers electrical energy into light and heat energy
Electrical energy (energy in) Light energy + Heat energy (Energy out)
We write these as Energy transfer diagrams:
Electrical energy —» Light energy + Heat Energy
Now write down energy transfer diagrams for these:
Useful and wasted energy- Sankey diagrams
For each of these devices, one form of energy (out) is useful and the other is wasted (not useful), for example, for the light bulb, we need the Light energy (useful energy), not the Heat energy (wasted).
We use a Sankey diagram to show these. A Sankey diagram is a scale diagram showing how much of each we get.
The total Energy out is Equal to the Energy in- No energy is lost or created.
Efficiency is how good something is at doing its job, for a light bulb, this is how good it is at producing light.
A more efficinet light bulb produces more light and less heat.
Energy efficiency = Useful energy out/Total Energy in x 100%
So for the bulb above Efficiency = 20/80 X 100%
Energy saver bulbs are said to be more Energy efficient. What does this mean in terms of how much Light they produce compared to Heat energy?