Electrical appliances
Many electrical appliances used in the home transfer electrical The capacity for doing work. to other useful forms.
| Appliance | Useful energy | Wasted energy |
| Electric kettle | Energy that heats the water | Thermal energy store heating the kettle and infrared radiation transferred to the surroundings |
| Hairdryer | Thermal energy store heating the air and kinetic energy of the fan that blows the air | Sound radiation, thermal energy store heating the hairdryer and infrared radiation transferred to the surroundings |
| Light bulb | Light radiation given out by the hot filament | Infrared radiation transferred to the surroundings |
| TV | Light radiation that creates images for the user and sound radiation that creates audio for the user | Thermal energy store heating the TV set and infrared radiation transferred to the surroundings |
| Appliance | Electric kettle |
|---|---|
| Useful energy | Energy that heats the water |
| Wasted energy | Thermal energy store heating the kettle and infrared radiation transferred to the surroundings |
| Appliance | Hairdryer |
|---|---|
| Useful energy | Thermal energy store heating the air and kinetic energy of the fan that blows the air |
| Wasted energy | Sound radiation, thermal energy store heating the hairdryer and infrared radiation transferred to the surroundings |
| Appliance | Light bulb |
|---|---|
| Useful energy | Light radiation given out by the hot filament |
| Wasted energy | Infrared radiation transferred to the surroundings |
| Appliance | TV |
|---|---|
| Useful energy | Light radiation that creates images for the user and sound radiation that creates audio for the user |
| Wasted energy | Thermal energy store heating the TV set and infrared radiation transferred to the surroundings |
The greater the amount of the supplied electrical energy transferred to useful energy stores, the more efficient the device will be. This can be shown in an energy transfer diagram or A diagram showing the flow of energy in a process. The width of the arrows indicates the relative amounts of energy involved..
Sankey diagrams
Sankey diagrams show the energy transfers in a system:
- the total energy transferred into the system is shown as an arrow
- this arrow splits into narrower arrows showing other transfers
Sankey diagrams are most useful when the amount of energy in each of the energy sources is known.
The width of the arrow is drawn to scale to show the amount of energy. Sankey diagrams show that the total energy transferred into a system is equal to the useful energy transferred plus the energy dissipated or 'wasted'. This confirms that energy is conserved.
Learn more on domestic uses and safety in this podcast
Listen to the full series on 大象传媒 Sounds.