Semi-conductors find wide application in designing electronic counters, because they react to all kinds of radiations. (Where?One of the main engineering problems which could be solved by using semi-conductor was converting heat into electricity without using boilers or other machines. (What?).​

Semi-conductors find wide application in designing electronic counters because they react to all kinds of radiations. They are typically used in the (where) part of the question to detect and measure the presence of radiation.

Semi-conductors are materials that have electrical properties between those of conductors (like metals) and insulators (like rubber). They have the ability to conduct electricity under certain conditions, making them very useful in electronics.

In the case of electronic counters, semi-conductors are used to detect and measure radiation. Different types of radiation, such as alpha particles, beta particles, and gamma rays, can interact with a semi-conductor and cause it to produce electrical signals. These signals can then be used to count and measure the intensity of the radiation.

One example of where semi-conductors are used in electronic counters is in Geiger-Muller tubes. These tubes contain a gas-filled chamber with a wire electrode, and the walls of the chamber are coated with a layer of semi-conductor material. When a radiation particle passes through the chamber, it ionizes the gas molecules, creating an electrical discharge. This discharge is then detected and measured by the semi-conductor material, allowing for the counting and measurement of radiation.

Now, let's move on to the second part of the question: "One of the main engineering problems which could be solved by using semi-conductor was converting heat into electricity without using boilers or other machines." This concept is known as thermoelectric conversion.

Thermoelectric conversion refers to the process of converting heat energy into electrical energy directly, without the need for traditional energy conversion methods such as boilers or turbines. This can be accomplished using a device called a thermoelectric generator, which relies on the principle of the Seebeck effect.

The Seebeck effect states that when two dissimilar metals, or semi-conductors, are joined together to form a circuit and there is a temperature difference between the two junctions, a potential difference, or voltage, is created across the circuit. This potential difference can then be used to generate electric current.

By utilizing semi-conductors with appropriate properties, thermoelectric generators can convert waste heat from various sources, such as industrial processes or car engines, into useful electrical power. This offers a way to harness and utilize energy that would otherwise go to waste, providing an efficient and environmentally friendly energy generation method.

In conclusion, semi-conductors are widely used in designing electronic counters because they can react to different types of radiation, allowing for the measurement and detection of radiation. Additionally, semi-conductors can be used to solve engineering problems, such as converting heat into electricity without the need for boilers or other machines, through thermoelectric conversion. This demonstrates the versatility and importance of semi-conductors in various technological applications.