A gas is contained in a metallic cylinder fitted with a piston.The piston is suddenly moved in to compress the gas and is maintained at this position. As time passes the pressure of the gas in the cylinder

Options

A. increases
B. decreases
C. remains constant
D. increases or decreases depending on the nature of the gas.

Explanation

To solve the problem, we need to analyze the situation step by step:

### Step 1: Understand the System
We have a gas in a metallic cylinder with a piston. When the piston is suddenly moved downwards, the gas is compressed, which means the volume of the gas decreases.

**Hint:** Remember that compressing a gas reduces its volume.

### Step 2: Identify the Conditions
After the piston is moved, it is maintained in that position. This means that the volume of the gas is now constant, but the gas is still subject to changes over time.

**Hint:** The volume of the gas remains constant after compression.

### Step 3: Heat Transfer in the Metallic Cylinder
Since the cylinder is made of metal, which is a good conductor of heat, any heat generated by the compression of the gas will be transferred to the surroundings.

**Hint:** Metals conduct heat well, allowing heat to escape from the system.

### Step 4: Effect of Heat Loss on Temperature
As time passes, the heat generated in the gas will radiate away, leading to a decrease in the temperature of the gas.

**Hint:** Heat loss from the gas leads to a decrease in temperature.

### Step 5: Relate Pressure, Volume, and Temperature
According to the ideal gas law, \( PV = nRT \), where:
- \( P \) = pressure
- \( V \) = volume
- \( n \) = number of moles of gas (constant)
- \( R \) = ideal gas constant (constant)
- \( T \) = temperature

Since the volume \( V \) is constant and the number of moles \( n \) and \( R \) are also constant, any change in temperature \( T \) will directly affect the pressure \( P \).

**Hint:** The ideal gas law relates pressure, volume, and temperature.

### Step 6: Analyze the Impact of Decreased Temperature
As the temperature \( T \) decreases, the pressure \( P \) must also decrease because they are directly proportional when volume is constant.

**Hint:** If temperature decreases, pressure must also decrease if volume remains constant.

### Conclusion
Therefore, as time passes after the piston is moved to compress the gas, the pressure of the gas in the cylinder decreases.

**Final Answer:** The pressure of the gas in the cylinder decreases over time.

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