Energy Transfers Flashcards
(19 cards)
What does temperature indicate?
How hot something is
Temperature is measured in degrees Celsius (°C)
How is internal (thermal) energy measured?
In joules (J)
Internal energy refers to the total energy contained within an object due to its temperature and state.
What factors determine the amount of thermal energy stored in an object?
- Temperature
- Material it is made from
- Mass
These factors influence the internal energy of the object.
What happens when two objects are at different temperatures?
Energy is transferred from the hotter object to the cooler one until they reach the same temperature.
Can evaporation occur at any temperature?
Yes
Evaporation involves the fastest-moving particles escaping to form a gas.
What effect does evaporation have on the temperature of the remaining liquid?
It lowers the temperature of the remaining liquid.
In which states of matter does conduction occur?
Solids and liquids
Conduction is less effective in liquids and gases.
What is an insulator?
Something that does not conduct heat very well
Insulators include liquids, gases, and solids with trapped air.
What is convection?
The transfer of heat in fluids (liquids and gases)
It involves the movement of particles and the establishment of convection currents.
What happens when part of a fluid is heated?
The particles spread further apart, and the fluid becomes less dense, causing it to rise.
How does infrared radiation transfer energy?
Through empty space and transparent materials
It does not require the movement of particles.
What are good emitters and absorbers of radiation?
Dark, dull surfaces
Light, shiny surfaces are good at reflecting radiation.
What is power?
The rate at which energy is transferred
Power is measured in watts (W) or kilowatts (kW).
How is efficiency calculated?
efficiency = (useful energy transferred / total energy supplied) × 100%.
What is a kilowatt-hour?
The amount of energy transferred when a one kW appliance is used for one hour.
What is payback time?
The time taken for the cost of installation to be matched by the money saved
payback time = change of cost / yearly savings.
What makes a measurement accurate?
Being close to the true value.
What is precision in measurements?
Obtaining similar results from several measurements of the same thing.
Can precise measurements be inaccurate?
Yes, if the measuring instrument was not set up correctly.
