A sealed, insulated container contains a battery, motor and paddle in water. The paddle starts and finishes at rest. The battery chemical store decreases by 800 J. No other non-thermal store changes. Which describes the overall change?
Thermal stores gain 800 J800\ \mathrm{J}800 J; total energy is unchanged
Thermal stores gain 800 J800\ \mathrm{J}800 J; total energy increases
Thermal stores lose 800 J800\ \mathrm{J}800 J; total energy decreases
Thermal stores lose 800 J800\ \mathrm{J}800 J; total energy is unchanged
115 exam-style questions on Edexcel GCSE Physics 8.1 Energy transfers and work, covering 8.1.1 Energy stores and transfer diagrams, 8.1.2 Ways of changing a system's energy, and 8.1.3 Work done by forces. Each one has a worked solution and a mark scheme showing where the marks go.