`DeltaE` is always positive when

Options

A. System absorbs heat and work is done on it
B. System emits heat and work is done by it
C. System emits heat and not work is done on it
D. System absorbs heat and work is done by it

Answer

To determine when ΔE (the change in internal energy) is always positive, we need to analyze the relationship between heat (Q) and work (W) in the context of the first law of thermodynamics, which states:

ΔE = Q + W

Where:
- ΔE = change in internal energy of the system
- Q = heat added to the system (positive if absorbed, negative if emitted)
- W = work done on the system (positive if done on the system, negative if done by the system)

### Step-by-Step Solution:

1. **Understanding ΔE**:
- ΔE represents the change in internal energy of a system. For ΔE to be positive, the sum of heat and work must be greater than zero.

2. **Heat Supply to the System (Q)**:
- When heat is supplied to the system, it is considered positive (Q > 0). This means that the system is absorbing energy.

3. **Work Done on the System (W)**:
- Work done on the system is also considered positive (W > 0). This means that energy is being added to the system through work.

4. **Combining Q and W**:
- For ΔE to be positive, both Q and W must be positive. Therefore, if the system absorbs heat and work is done on it, we can express this as:
- ΔE = Q (positive) + W (positive) = positive

5. **Conclusion**:
- The condition for ΔE to always be positive is that the system must absorb heat (Q > 0) and work must be done on the system (W > 0).

### Final Answer:
ΔE is always positive when the system absorbs heat and work is done on the system.