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Energy and efficiency
- Conservation of energy
- Energy cannot be created or destroyed, only transferred
- When energy is transferred, only part of it may be usefully transferred --> the rest is wasted
- Wasted energy is transferred to its surroundings, which become warmer --> wasted energy becomes more spread out --> less usefel
- Sankey diagram
- Shows useful
and wasted
forms of energy
- Shows how
efficient an
appliance is
- Shows useful
and wasted
forms of energy
- Wasted energy is transferred to its surroundings, which become warmer --> wasted energy becomes more spread out --> less usefel
- When energy is transferred, only part of it may be usefully transferred --> the rest is wasted
- Energy cannot be created or destroyed, only transferred
- Efficiency = useful energy out/total energy in x 100%
- Usefulness of electrical appliances
- Electrical appliances transfer energy at the flick of a switch
- You can calculate how much energy is transferred
- E = P x t
- Amount of energy transferred from the mains electricity (kWh and J)
- Amount of energy transferred from the mains electricity (kWh and J)
- E = P x t
- You can calculate how much the appliance costs to run
- Total cost of bill = no. of kWh used x cost per kWh (rate)
- Total cost of bill = no. of kWh used x cost per kWh (rate)
- You can calculate how much energy is transferred
- Power is the rate at which the object transfers energy
- Cost effectiveness
- Getting the best value for money
- Payback time is the time it takes for
an appliance/installation to pay for
itself in terms of energy savings
- Getting the best value for money
- Electrical appliances transfer energy at the flick of a switch
- Efficiency = useful power out/total power in x 100%
- Input energy = useful energy + wasted energy
- Forms of energy
- Stored energies
- Gravitational potential
- A falling object transfers g.p. to kinetic energy
- A falling object transfers g.p. to kinetic energy
- Elastic potential
- Chemical
- Gravitational potential
- Stored energies
- Improving effiency
- Reduce:
- Friction (e.g. lubricating moving parts)
- Electrical resistance (e.g. less resistant wires)
- Noise due to vibrations (e.g. cut out noise)
- Air resistance (e.g. streamline the shapes of moving objects)
- Friction (e.g. lubricating moving parts)
- Reduce:
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