Energy Efficiency and Specific Heat Capacity Flashcards
How does draught-proofing prevent heat loss?
Reduces heat loss by convection, as cold air cannot blow in.
How does loft insulation prevent heat loss?
Reduces heat loss by conduction and convection through the ceiling.
How does cavity wall insulation prevent heat loss?
Reduces convection, conduction and radiation between the bricks.
How do thick curtains prevent heat loss?
Reduces convection because of an air gap. Also reduces conduction and radiation.
How does a hot water tank jacket prevent heat loss?
Reduces conduction and radiation around the tank.
What does a U-value mean?
The lower the U-value, the better the insulator.
What is specific heat capacity?
Specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1C.
What is the unit of specific heat capacity?
J/kgC
Why do materials in heaters have high specific heat capacities?
To store large amounts of energy.
Why is water ideal for central heating systems?
- High SHC
2. Liquid, so can be pumped around
What are the nine types of energy?
Electrical Light Sound Kinetic Nuclear Thermal Gravitational Potential Elastic Potential Chemical
What is conservation of energy principle?
Energy can be transferred usefully from one form to another, stored or dissipated, but can never be created or destroyed.
What is the principle of energy utility?
Energy is only useful when it can be converted from one form to another.
What is the formula for energy efficiency?
Useful energy out
Efficiency = Total energy in
What is most energy wasted as?
Heat, from friction usually.
What are the advantages of low-energy bulbs?
- More efficient
2. More cost-effective
What are the advantages of LEDs?
- Most efficient
2. Lasts longer
What are the disadvantages of LEDs?
- Expensive
2. Not as much light given out
How do heat exchangers reduce the amount of heat energy lost?
Pumping a cool fluid through the escaping heat to be reused or transferred.
On a Sankey diagram, what does a thicker arrow represent?
More energy transferred.
What is a kilowatt-hour?
The amount of electrical energy used by a 1kW appliance left on for 1 hour.
What is power measured in?
Watts or kilowatts.
What needs to be considered when comparing appliances?
- Energy efficiency
- Cost-effectiveness
- Practical advantages and disadvantages
How does electricity affect living standards?
- Refrigeration (food and vaccines)
- Hospitals
- Communications
- Electrical appliances
