Apply the first law of thermodynamics to HL questions on heat, work and internal energy, using sign conventions and PV diagrams to analyse gases and cycles.
This question is in two parts
With reference to the first law of thermodynamics, explain for the change of state A to B, why energy is transferred from the surroundings to the gas.
Work is done by the gas because there is an increase in volume / gas expands.
So W is positive.
Delta U is greater than zero because P is constant and V increases.
From the first law, Q = Delta U + W, so Q is positive, which means energy is transferred into the gas.