8.1 Energy Sources

Which energy source primarily relies on the conversion of sunlight into electricity using semiconductors?

A. Wind Energy

B. Geothermal Energy

C. Solar Energy

D. Tidal Energy

What is a primary environmental concern associated with hydroelectric dams?

A. Air pollution

B. Habitat destruction

C. Nuclear waste

D. Greenhouse gas emissions

Which energy source involves harnessing heat from the Earth's core?

A. Solar Energy

B. Biomass

C. Geothermal Energy

D. Wind Energy

Which of the following is NOT a type of fossil fuel?

A. Coal

B. Oil

C. Uranium

D. Natural Gas

What is the primary challenge associated with wind energy?

A. Radioactive waste

B. Intermittency

C. Greenhouse gas emissions

D. Habitat destruction

a) A photovoltaic cell with an efficiency of 20% is exposed to sunlight with an intensity of 600 W/m^2. Calculate the power output per square metre of the cell. [2]

b) If the cell has an area of 1.5 m^2, determine the total power output of the cell. [2]

a) A wind turbine with a blade length of 50 m rotates at 15 revolutions per minute (rpm). Calculate the linear speed of the tip of the blade. [2]

b) If the wind speed is 12 m/s, and the turbine operates at 40% efficiency, determine the power extracted from the wind by the turbine. Assume air density to be 1.225 kg/m^3. [2]

a) A geothermal plant extracts 5000 kg of steam per hour from the Earth's core at a temperature of 400°C and uses it to heat water from a river at 20°C. Calculate the heat energy transferred from the steam if its specific heat capacity is 2.1 J/g°C. [2]

b) If the geothermal plant operates at an efficiency of 30%, determine the useful energy output from the extracted heat. [2]

a) Explain the working principle of photovoltaic cells in converting sunlight into electricity. [3]

b) What challenges are faced in terms of energy storage for solar farms? [2]

c) Calculate the energy output of a solar farm if it has an efficiency of 20% and receives sunlight with a power of 600 W/m^2 over an area of 2000 m^2 for 5 hours. [3]

a) Describe the environmental impact of wind farms. [3]

b) If a wind turbine has a blade length of 50m, calculate the swept area of the turbine. [2]

c) Given that the air density is 1.225 kg/m^3 and the wind speed is 10 m/s, calculate the power available in the wind that can be harnessed by the turbine. [3]