The principle of controlled chain reaction is used in.

Options

A. atomic energy reactor
B. atom bomb
C. the core of sun
D. artificial radioactivity

Answer

To solve the question regarding where the principle of controlled chain reaction is used, we can follow these steps:

### Step 1: Understand the concept of a controlled chain reaction
A controlled chain reaction is a process where the rate of reaction is managed to produce energy at a steady rate. This is crucial in applications where consistent energy output is required, such as in nuclear reactors.

**Hint:** Think about systems where energy needs to be produced steadily over time rather than in a sudden burst.

### Step 2: Identify applications of controlled chain reactions
The most prominent application of controlled chain reactions is in nuclear reactors. In these reactors, fissionable materials (like uranium-235) undergo fission, releasing energy. The reaction is controlled using materials that absorb excess neutrons (like cadmium rods), preventing the reaction from escalating uncontrollably.

**Hint:** Consider where nuclear reactions are harnessed for energy production rather than for explosive purposes.

### Step 3: Eliminate incorrect options
1. **Atomic Bomb**: This utilizes an uncontrolled chain reaction, leading to an explosive release of energy.
2. **Core of the Sun**: The Sun primarily undergoes nuclear fusion, not fission, and while fusion can be controlled in theory, it is not the same as a fission-based controlled chain reaction.
3. **Artificial Radioactivity**: This typically involves uncontrolled reactions as well.

**Hint:** Focus on the definitions of each term and how they relate to the concept of control in reactions.

### Step 4: Conclude with the correct answer
The only application that fits the description of a controlled chain reaction is the atomic energy reactor. Therefore, the correct answer is:

**Answer: Atomic Energy Reactor**

### Summary of Steps:
1. Understand controlled chain reactions.
2. Identify applications (nuclear reactors).
3. Eliminate incorrect options (atomic bomb, core of the sun, artificial radioactivity).
4. Conclude with the correct answer.