Question

If 150 J of heat is added to a system and the work done by the system is 110 J, then the change in internal energy will be

• A. 40 J
• B. 110 J
• C. 150 J
• D. 260 J

Hint:

The first law of thermodynamics relates the change in internal energy to the heat added and the work done by the system. Remember that work done by the system is subtracted from the heat added to find the change in internal energy.

Answer 1

The Correct Option is A

To determine the change in internal energy of the system, we use the first law of thermodynamics, which is given by:

ΔU = Q - W

where:

• ΔU is the change in internal energy.
• Q is the heat added to the system.
• W is the work done by the system.

According to the problem:

• Q = 150 J (heat added to the system)
• W = 110 J (work done by the system)

Substituting these values into the equation:

ΔU = 150 J - 110 J

Therefore, the change in internal energy is:

ΔU = 40 J

Thus, the change in internal energy of the system is 40 J.

Answer 2

According to the first law of thermodynamics: \[ \Delta U = Q - W \] where:
- \( \Delta U \) is the change in internal energy,
- \( Q \) is the heat added to the system,
- \( W \) is the work done by the system. Given:
- \( Q = 150 \, \text{J} \),
- \( W = 110 \, \text{J} \). Substituting the values into the formula: \[ \Delta U = 150 \, \text{J} - 110 \, \text{J} = 40 \, \text{J} \]
Thus, the change in internal energy is \( 40 \, \text{J} \). Therefore, the correct answer is: \[ \text{(A) } 40 \, \text{J} \]