The entropy of the universe always:
Correct answer: B. Increases
- A. Decreases
- B. Increases
- C. Remains the same
- D. Both A and B
Explanation
The energy of the universe increases because energy never flows uphill spontaneously. Energy always flows downhill, and this causes an increase in entropy. Entropy is the spreading out of energy, and energy tends to spread out as much as possible. It flows spontaneously from a hot (i.e. highly energetic) region to a cold (less energetic) region. As a result, energy becomes evenly distributed across the two regions, and the temperature of the two regions becomes equal. The same thing happens on a much larger scale. The Sun and every other star are radiating energy into the universe. Mathematically, consider the total energy q that is transferred from a hot region at temperature T1 to a cold region at temperature T2. The entropy S1 of the hot region is defined as S1=qT1 The entropy S2 of the cold region is S2=qT2 Therefore, during the energy transfer, the change in entropy is ΔS=S2−S1 =qT2−qT1 =q(T2−T1) Since T2<T1,1T2>1T1 and ΔS is positive. The total entropy of the system increases. Since energy never flows spontaneously in the other direction, the total entropy of the universe is always increasing.
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