Question

If heat flows into a system and the system does work on the surroundings, what will be the signs on q and w? Select the correct answer below O positive q, positive w O positive q, negative w O negative q, positive w O negative q, negative w

Answer 1

q = Positive

w = Negative

Step-by-step explanation:

As per first law of thermodymanics,

ΔE = q + w

Where,

ΔE = Change in internal energy

q = Heat absorbed or heat released by the system

w = Work done

Sign conventions are used for heat transfer and work done during a thermodynamics process.

Sign convention for Heat transfer

• q is positive when heat is added to the system or heat absorbed by the system this is because energy of the system is increased.
• q is negative when heat is withdrawn from the system or heat released by the system.

Sign convention for Work done

• w is positive if work is done on the system or work is done by the surroundings
• w is negative if work is done on the system or work is done on the surrounding.

In the given question, work is done on the surroundings so, w is negative.

Heat flows into a system or in other word heat is added to the system,

So q is positive.