The energy supply being cut-off, an electric heater element cools down to a temperature of its surroundings but it will not cool further because

Options

A. supply is cut off
B. it is made of metal
C. surrounding are radiating
D. elements and surrounding have same temperature

Answer

To solve the question, we need to understand the principles of heat transfer and thermal equilibrium. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Understanding Heat Transfer
Heat transfer occurs when there is a temperature difference between two objects. The object at a higher temperature will transfer heat to the object at a lower temperature until they reach thermal equilibrium.

**Hint:** Remember that heat flows from hot to cold until temperatures equalize.

### Step 2: Initial Condition of the Heater
When the electric heater is operational, it is at a higher temperature (e.g., 100°C) compared to its surroundings (e.g., 20°C). This temperature difference causes the heater to lose heat to the surrounding air.

**Hint:** Consider what happens when you turn off a heater; it starts to cool down.

### Step 3: Cooling Process
As the heater cools down, it transfers heat to the surrounding air. This process continues until the temperature of the heater decreases to match the temperature of the surrounding air.

**Hint:** Think about how the surrounding air temperature changes as the heater cools.

### Step 4: Reaching Thermal Equilibrium
When the heater's temperature equals the surrounding temperature (let's say both become 30°C), they are in thermal equilibrium. At this point, there is no longer a temperature difference to drive heat transfer.

**Hint:** What happens to heat transfer when two objects are at the same temperature?

### Step 5: Conclusion on Further Cooling
Since there is no temperature difference (ΔT = 0), no heat transfer occurs. Therefore, the heater cannot cool down any further than the temperature of its surroundings.

**Hint:** Reflect on the concept of equilibrium; it stops further changes in temperature.

### Final Answer
The electric heater element will not cool further because the elements and surroundings have the same temperature, which means there is no temperature difference to facilitate heat transfer. Thus, the correct answer is option 4: "elements and surroundings have the same temperature."