iGCSE Physics (0625) 1.7.3 Energy resources-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
In $2000$, coal accounted for $50\%$ ($100\% – 50\%$) of energy, while in $2024$, it decreased to approximately $28\%$ ($78\% – 50\%$).
Wind is the renewable resource in this set; its usage was $0\%$ in $2000$ and increased to $22\%$ ($100\% – 78\%$) in $2024$.
Gas remained constant at $50\%$ in both years, serving as a baseline for comparison.
Therefore, the percentage of coal used has seen a significant decrease, while renewable energy has seen an increase.
This makes Row C the correct description of the shifts in the island’s energy resource composition.
▶️ Answer/Explanation
Detailed solution:
Generating electricity from coal involves burning the fuel to release thermal energy, which is used in a boiler to turn water into high-pressure steam.
This steam then expands through a turbine, converting thermal energy into kinetic energy ($E_{k}$) to drive a generator.
In contrast, tidal (B) and hydroelectric (C) schemes use the gravitational potential energy ($\Delta E_{p} = mg\Delta h$) of water to turn turbines directly without heat.
Wind turbines (D) harness the kinetic energy of air directly, requiring no thermal cycle or steam production.
Therefore, only the combustion of fossil fuels like coal utilizes a boiler-steam-turbine sequence.
▶️ Answer/Explanation
Detailed solution:
Chemical energy is energy stored in the bonds of chemical compounds, which is released during a chemical reaction (like combustion).
Biofuel, coal, and oil are all forms of fuel that release energy through burning, meaning they are stores of chemical energy.
Nuclear fuel, such as uranium, does not release energy through chemical bonds but through nuclear fission or fusion.
In these processes, energy is released from the nucleus of the atom, which is defined as a store of nuclear energy.
Therefore, nuclear fuel is the only resource listed that does not contain a store of chemical energy.
Option C is the correct choice as it identifies nuclear fuel as a non-chemical energy store.