P2 - Energy Transfer By Heating Flashcards
How do you make a test with rods of different materials as conductors fair?
Rods need to be same width and length.
Each rod coated with a thin layer of wax near one end. I coated ends are heated together.
What is thermal conductivity?
Energy transfer by conduction through a material.
How does thermal conductivity affect energy?
The greater the thermal conductivity of a material, the more energy per second it transfers by conduction.
What are insulators used for?
Keep you warm in winter, loft floor reduce energy transfer.
What are the properties of insulators?
Low thermal conductivity so energy transfer through them is as low as possible.
I get does the transfer through a layer of insulating material depend on?
Temperature difference across the material
Thickness of the material
Thermal conductivity of the material.
How do you reduce energy transfer?
The thermal conductivity of an insulating material should be as low as possible
The thickness of the insulating layer should be as thick as practically possible
When a substance is heated, what does the temperature rise depend on?
The amount of energy supplied to it
The mass of the substance
What the substance is
What is specific heat capacity?
The energy needed to raise the temperature of 1kg of the substance by 1•C
What is the unit of specific heat capacity?
J/kg•C
What is the equation for energy transferred?
Energy transferred = mass * specific heat capacity * temperature change
Joules = kilograms * joules per kilogram per degree Celsius * degree Celsius
What is the required practical for measuring specific heat capacity?
Heat a metal block of know mass. You need to use a thermometer and a top-pan balance. Use the joule meter to measure the energy supplied to the block. Use he thermometer to measure temperature rise.
Replace the clock with an equal mass of water in a suitable container. Measure the temperature rise if the water when the same amount of energy is supplied to it by the heater.
What are storage heaters?
A storage heater uses electricity at night to beat concrete clocks in the heater. Energy transfer from the bricks keeps the room warm. The bricks have a high specific heat capacity so they store lots of energy. They warm up slowly when the heater on and cool down slowly when it is off.
How are houses headed?
Has heaters
Electric heated
Oil central heating
Gas central heating
Solid fuel in stoves
Solid fuel is fireplaces
How do you reduce energy loss from the home?
Loft insulation
Cavity wall insulation
Thicker bricks with lower thermal conductivity
Double glazed windows
Aiming um foul between a radiator panel and the wall.
How does loft insulation work?
Loft insulation such as fiberglass reduced the rate if energy transfer through the roof. It is a good insulator and the air between fibers reduced the rate of energy transfer through conduction.
How does cavity wall insulation work?
Reduces rate of energy transfer through the outer walls of the house. The cavity of an outer wall is the space between the two layers of brick making to the wall and insulation id pumped into the cavity making it a better insulator.
How does aluminum foil work?
It goes between a radiator panel and the wall reflects radiation away from the wall and so reduced the rate of energy transfer by radiation
How do double glazed windows work?
They have two glass panes with dry air or a vacuum between them. The thicker there glass and the lower it’s thermal conductivity, the slows the transfer of energy. Dry air is a good insulator.
How do external walls work?
If the external walls if a warm building have thicker bricks and lower thermal conductivity, the rate of transfer of energy from the inside of the building to get outside will be lower and the cost of heating will be less.
How do solar panels work?
They absorb infrared radiation from the Sun and are used to generate electricity directly or to heat water directly.
