The resistance of mercury becomes almost zero at:

Options

A. 4 K
B. 10 K
C. 20 K
D. 25 K

Answer

To determine the temperature at which the resistance of mercury becomes almost zero, we can follow these steps:

### Step 1: Understand the Concept of Superconductivity
Superconductivity is a phenomenon where a material exhibits zero electrical resistance when cooled below a certain critical temperature. This critical temperature varies for different materials.

**Hint:** Remember that superconductivity is characterized by the absence of electrical resistance.

### Step 2: Identify the Critical Temperature for Mercury
Mercury is known to become a superconductor at a specific low temperature. Historical experiments have shown that the critical temperature for mercury is approximately 4.12 Kelvin.

**Hint:** Look for the specific temperature range where superconductivity occurs in metals, especially mercury.

### Step 3: Analyze the Given Options
The options provided are:
1. 4 Kelvin
2. 10 Kelvin
3. 20 Kelvin
4. 25 Kelvin

From our knowledge of mercury's superconductivity, we can see that the closest option to the critical temperature of mercury (4.12 K) is 4 Kelvin.

**Hint:** Compare the critical temperature of mercury to the options given to find the closest match.

### Step 4: Conclusion
Based on the information gathered, the resistance of mercury becomes almost zero at approximately 4 Kelvin.

**Final Answer:** The resistance of mercury becomes almost zero at **4 Kelvin**.