iGCSE Physics (0625) 1.7.3 Energy resources-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
The Sun is the primary source of energy for most Earth resources, but there are specific exceptions.
Wind energy is driven by the Sun, as solar radiation causes uneven heating of the atmosphere, creating pressure differences.
Geothermal energy originates from radioactive decay and residual heat within the Earth’s core, not the Sun.
Nuclear fuel (such as Uranium) is derived from elements present during the Earth’s formation and is not a solar product.
According to the syllabus, only geothermal, nuclear, and tidal resources do not depend on the Sun.
Therefore, out of the three listed, only wind ($2$) obtains its energy from solar radiation, making D the correct choice.
▶️ Answer/Explanation
Detailed solution:
Efficiency is the ratio of useful energy output to the total energy input, mathematically defined as $Efficiency = \frac{Useful\ Energy\ Output}{Total\ Energy\ Input} \times 100\%$.
According to the fundamental principle of conservation of energy, energy cannot be created, meaning an electrical device can never output more energy than it initially takes in.
Therefore, the absolute theoretical maximum efficiency of any machine or electrical system is exactly 100%.
In reality, practical efficiency is always less than 100% due to energy being dissipated to the surroundings, usually as thermal energy.
A calculated efficiency of 102% implies that the device is generating more energy than it consumes, which is physically impossible and indicates a calculation error.
▶️ Answer/Explanation
Detailed solution:
The Sun is the primary source of energy for most Earth-based resources, including wind.
Wind is produced by the uneven heating of the Earth’s atmosphere by solar radiation.
This temperature differential causes air to move, creating kinetic energy that we harness as wind power.
In contrast, geothermal energy originates from the Earth’s internal heat, and nuclear energy comes from atomic nuclei.
Tidal energy is primarily driven by the gravitational pull of the Moon and the Sun, not solar radiation.
Therefore, according to the syllabus, geothermal, nuclear, and tidal are the three specific exceptions.
As a result, wind is the only resource listed that is directly derived from solar energy.