What happens to the internal energy of an ideal gas during an isothermal expansion?

Answer and explanation

Correct answer: A. It remains constant

  1. Step 1: For an ideal gas, internal energy U depends solely on absolute temperature T: U = (3/2) n R * T.
  2. Step 2: In an isothermal process, Delta T = 0, so Delta U = 0.
  3. Step 3: Heat absorbed by the gas is converted completely into work done: Q = W.
  4. Step 4: Thus internal energy remains constant.
Answer
It remains constant.
Why not the others: 'It increases because volume expands' ignores that intermolecular potential energy is zero in ideal gases; 'It decreases because work is done' overlooks that heat input balances work; 'It drops to zero' confuses delta with absolute zero.

Practise more Classical Mechanics and Electromagnetism.

Free questions with an explanation for every one, and full timed Qatar Senior Secondary Certificate (Thanaweya) mock tests.

All Classical Mechanics and Electromagnetism questionsTake a mock test

More Classical Mechanics and Electromagnetism questions