A system absorbs reversibly 600 J of heat and performs 250 J of work. The increase in the internal energy of system is :-

Options

A. 850 J
B. 250 J
C. 600 J
D. 350 J

Answer

To find the increase in the internal energy of the system, we can use the first law of thermodynamics, which states:

\[ \Delta U = Q - W \]

Where:
- \(\Delta U\) = change in internal energy
- \(Q\) = heat absorbed by the system
- \(W\) = work done by the system

### Step-by-Step Solution:

1. **Identify the Heat Absorbed (Q)**:
The system absorbs 600 J of heat. Therefore, we have:
\[ Q = 600 \, \text{J} \]

2. **Identify the Work Done (W)**:
The system performs 250 J of work. According to the convention used in thermodynamics, work done by the system is considered negative. Thus:
\[ W = -250 \, \text{J} \]

3. **Apply the First Law of Thermodynamics**:
Substitute the values of \(Q\) and \(W\) into the equation for change in internal energy:
\[ \Delta U = Q - W \]
Substituting the known values:
\[ \Delta U = 600 \, \text{J} - (-250 \, \text{J}) \]

4. **Simplify the Equation**:
When you subtract a negative, it becomes addition:
\[ \Delta U = 600 \, \text{J} + 250 \, \text{J} \]
\[ \Delta U = 850 \, \text{J} \]

5. **Final Result**:
The increase in the internal energy of the system is:
\[ \Delta U = 850 \, \text{J} \]

### Summary:
The increase in the internal energy of the system is **850 J**.

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