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Physics: Energy, Climate, and Sustainability - Renewable and Non-renewable Energy Resources

Grade 8IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Renewable energy resources are those that are replenished naturally over short periods, such as solar, wind, hydroelectric, tidal, and geothermal energy. They generally have a lower environmental impact and do not emit CO2CO_2 during operation.

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Non-renewable energy resources, such as coal, oil, natural gas, and nuclear fuels, exist in finite amounts and cannot be replaced once consumed. Combustion of fossil fuels releases greenhouse gases like CO2CO_2, contributing to the enhanced greenhouse effect.

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The Law of Conservation of Energy states that energy cannot be created or destroyed, only transformed from one form to another. In any energy transfer, some energy is dissipated as non-useful forms, usually heat (QQ).

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Sustainability refers to using resources in a way that meets the needs of the present without compromising the ability of future generations to meet their own needs. This involves increasing the share of renewables in the global energy mix.

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Energy efficiency is a measure of how much 'useful' energy is obtained from a system compared to the total energy put in. Sankey diagrams are often used to visualize these energy transfers, where the width of the arrows represents the amount of energy.

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Power is the rate at which energy is transferred or work is done. It is measured in Watts (WW), where 1 W=1 J/s1\text{ W} = 1\text{ J/s}.

📐Formulae

Efficiency=(Useful Energy OutputTotal Energy Input)×100%\text{Efficiency} = \left( \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} \right) \times 100\%

P=EtP = \frac{E}{t}

W=F×dW = F \times d

ΔEp=mgh\Delta E_p = mgh

Ek=12mv2E_k = \frac{1}{2}mv^2

💡Examples

Problem 1:

A wind turbine captures 25,000 J25,000\text{ J} of kinetic energy from the wind every second. If it outputs 10,000 J10,000\text{ J} of electrical energy per second, calculate its efficiency.

Solution:

Efficiency=1000025000×100=40%\text{Efficiency} = \frac{10000}{25000} \times 100 = 40\%

Explanation:

To find the efficiency, we divide the useful energy output (10,000 J10,000\text{ J}) by the total energy input (25,000 J25,000\text{ J}) and multiply by 100100. The remaining 60%60\% of energy is typically lost as heat due to friction in the turbine's internal components.

Problem 2:

A solar panel system produces 1.2 kJ1.2\text{ kJ} of energy in 22 minutes. Calculate the power output of the system in Watts (WW).

Solution:

t=2×60=120 st = 2 \times 60 = 120\text{ s} E=1.2×1000=1200 JE = 1.2 \times 1000 = 1200\text{ J} P=1200120=10 WP = \frac{1200}{120} = 10\text{ W}

Explanation:

First, convert all units to SI (2 minutes=120 seconds2\text{ minutes} = 120\text{ seconds} and 1.2 kJ=1200 J1.2\text{ kJ} = 1200\text{ J}). Then use the power formula P=EtP = \frac{E}{t} to find the rate of energy transfer.

Problem 3:

In a hydroelectric power station, 500 kg500\text{ kg} of water falls from a height of 20 m20\text{ m}. Calculate the total gravitational potential energy available, assuming g=9.8 m/s2g = 9.8\text{ m/s}^2.

Solution:

Ep=mghE_p = mgh Ep=500×9.8×20E_p = 500 \times 9.8 \times 20 Ep=98000 JE_p = 98000\text{ J}

Explanation:

The energy available in the water is its gravitational potential energy. Using the mass (500 kg500\text{ kg}), gravity (9.8 m/s29.8\text{ m/s}^2), and height (20 m20\text{ m}), we calculate the total energy input before it is converted into kinetic energy and then electricity.