P2a-collecting energy from the sun

Question 1

What are some advantages of using photocells to provide electricity?

Answer 1

• low maintenance
• no need for power cables
• no need for fuel
• long life
• renewable energy resource
• no polluting waste

Question 2

What are some disadvantages of using photocells to provide electricity?

Answer 2

• no power at night

- no power in bad weather

Question 3

Describe how light produces electricity in a photocell

Answer 3

1) electrons absorbed by photocell
2) electrons knocked loose from silicon atoms in the crystal
3) electrons flow freely

Question 4

What does the current and power produced in a photocell depend on?

Answer 4

• light intensity
• surface area exposed
• distance from the light source

Question 5

In what ways can the sun be harnessed?

Answer 5

1) radiation from the sun can be absorbed by Surface and transferred into heat energy
2) produces convection currents(wind) to drive turbines
3) glass can be used to provide passive solar heating for buildings
4) light can be reflected to a focus by a curved mirror

Question 6

What are some advantages of using wind turbines?

Answer 6

• renewable

- no polluting waste

Question 7

What are some disadvantages of wind turbines?

Answer 7

• visual pollution
• dependency on wind speed
• appropriate space and position needed

Question 8

Why does passive solar heating work?

Answer 8

• glass is transparent to suns radiation
• heated surfaces emit infrared radiation of longer wavelength
• glass reflects this longer wavelength infrared

Question 9

What must an efficient solar collector do?

Answer 9

Track the position of the sun in the sky

Question 10

What do photocells do?

Answer 10

• transfer light into electricity
• produce direct current
• can operate in remote locations
• have a power or current in the same direction all the time