P2a Flashcards
(10 cards)
What do photocells do?
Transfer light into electricity.
Produce direct current meaning the current flows the same way around the circuit at all times.
Can operate in remote locations.
What are the advantages of using photocells to provide electricity?
Low maintenance. No need for power cables or fuel. Long life. Renewable energy resource so won't run out. No polluting waste.
What is the disadvantage of using photocells to provide electricity?
No power at night or in bad weather because there’s no sunlight.
How does light produce electricity in a photocell?
Energy is absorbed by the photocell. Electrons are knocked loose from the silicon atoms in the crystal. Electrons flow freely.
What does the current and power produced in a photocell depend on?
Light intensity - brighter light=more electricity.
Surface area exposed - bigger the cell, the more electricity it produces.
Distance from the light source - closer the cell, the more intense the light hitting it will be.
What are the four ways the sun’s energy can be harnessed?
Radiation from the sun can be absorbed by a surface and transferred into heat energy.
Energy from the sun heats the atmosphere which cause convection currents, which produce wind to drive turbines. They convert the kinetic energy of moving air into electricity.
Glass can be used to provide passive solar heating, when energy from the sun is used to heat something directly, for buildings.
Light can be reflected to a focus by a curved mirror. A single curved mirror can be used as a solar oven and large curved mirrors can be used to generate steam to produce electricity.
What are the advantages of wind turbines?
Wind power is renewable - the wind’s never going to run out.
Wind power doesn’t produce any polluting waste.
What are the disadvantages of wind turbines?
Visual pollution - they spoil the view.
Dependency on wind speed - Sometimes the wind isn’t fast enough to generate any power.
Appropriate space and position needed - they need to be spaced out and built in places that are windy enough.
Why does solar passive heating work?
GLASS IS TRANSPARENT TO SUN’S RADIATION, letting in heat and light from the sun, which is absorbed by things in a room, heating them up. The light from the sun has a shorter wavelength, so it can pass through the glass into a room.
HEATED SURFACES EMIT INFRARED RADIATION OF LONGER WAVELENGTH, which can’t escape through the glass as GLASS REFLECTS THE LONGER WAVELENGTH.
What must an efficient solar collector do?
Track the position of the sun in the sky, to capture the maximum amount of light and heat.
