Question 1: Define renewable energy sources and explain why they are considered sustainable.

Answer: Renewable energy sources are natural resources that are replenished naturally and can be used repeatedly without depleting. They are considered sustainable because they do not produce long-term environmental damage and are inexhaustible on a human timescale.

Question 2: List three examples of renewable energy sources commonly used today.

Answer: Solar power, wind power, hydroelectric power.

Question 1: Explain how solar panels convert sunlight into electricity.

Answer: Solar panels contain photovoltaic cells that absorb sunlight, causing electrons to move and generate an electric current through the photovoltaic effect.

Question 2: Describe the basic principle behind wind turbines generating electricity.

Answer: Wind turbines convert the kinetic energy of moving air into mechanical energy, which is then transformed into electrical energy by a generator.

Question 1: A solar panel has an area of 2 square metres and an efficiency of 15%. If the average solar irradiance is 1000 W/m², calculate the power output of the solar panel in watts.

Answer: Power = Solar irradiance × Area × Efficiency = 1000 W/m² × 2 m² × 0.15 = 300 W

Question 2: A wind turbine has a rotor diameter of 80 metres. Assuming the wind speed is 12 m/s, calculate the swept area of the rotor in square metres. Use the formula for the area of a circle: A = πr².

Answer: Radius r = diameter/2 = 40 m; Area = π × (40 m)² ≈ 3.1416 × 1600 ≈ 5026.5 m²

Question 1: Describe a basic experiment to demonstrate the effect of sunlight on a solar cell. Include key variables and safety precautions.

Answer: Place a solar cell in direct sunlight and connect it to a voltmeter to measure voltage output. Variables include light intensity, distance from light source, and angle of the solar cell. Safety precautions involve avoiding direct eye exposure to bright sunlight and ensuring the electrical connections are insulated to prevent shocks.

Question 1: A hydroelectric power station has a height difference of 50 metres and a flow rate of 10 cubic metres per second. Calculate the potential power output in watts, assuming the efficiency of the turbine is 90%. Use the formula: Power = ρghQη, where ρ = 1000 kg/m³ (density of water), g = 9.8 m/s², h = height difference, Q = flow rate, η = efficiency.

Answer: Power = 1000 kg/m³ × 9.8 m/s² × 50 m × 10 m³/s × 0.9 ≈ 4,410,000 W or 4.41 MW

Question 2: Identify two advantages and two disadvantages of using wind power as a renewable energy source.

Answer: Advantages: It is renewable and produces no greenhouse gases. Disadvantages: Wind power is intermittent and can be noisy or cause visual pollution.

Question 1: Explain how solar power is used in residential buildings to reduce energy costs and environmental impact.

Answer: Solar power systems installed on rooftops convert sunlight into electricity, reducing reliance on fossil fuels and lowering electricity bills, while also decreasing greenhouse gas emissions.

Question 2: Describe one recent technological advancement in renewable energy and its significance.

Answer: The development of more efficient perovskite solar cells, which provide higher energy conversion rates and lower production costs, enhancing the viability of solar energy worldwide.