First-Law Split Three-Row Scan - Heat & Thermodynamics Step by Step

The same heat input can split into work and internal energy in several exact ways. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Most energy can stay internal

A 20 joule input can split into 4 joules of work and 16 joules of internal-energy change.

Q_{\text{in}}=4\ \text{J}+16\ \text{J}=20\ \text{J}

The middle split still closes

The middle row uses 12 joules of work and 8 joules stored internally.

Q_{\text{in}}=12\ \text{J}+8\ \text{J}=20\ \text{J}

More work leaves less internal storage

The third row sends 16 joules to work and only 4 joules to internal energy. The total stays fixed.

\begin{array}{c|c|c}W&\Delta U&Q_{\text{in}}\\4\ \text{J}&16\ \text{J}&20\ \text{J}\\12\ \text{J}&8\ \text{J}&20\ \text{J}\\16\ \text{J}&4\ \text{J}&20\ \text{J}\\\end{array}