Question

What is heat generation in a solid? Give examples.

Short answer

Answer: Heat generation in a solid refers to the production of thermal energy within the material due to various physical and chemical processes. Examples of such processes include electrical resistance heating (e.g., Joule heating in metal wires), chemical reactions that produce heat (e.g., exothermic reactions in concrete curing), nuclear decay (e.g., heat generation in nuclear fuel rods), and frictional heating (e.g., heat generated by brakes in vehicles or drilling into solid materials).

Step-by-step solution

Definition of Heat Generation in a Solid

Heat generation in a solid occurs when energy is produced within the material due to various physical and chemical processes. This energy production causes an increase in the internal energy and temperature of the solid.

Example 1: Electrical Resistance Heating

When an electric current flows through a solid conductor, such as a metal wire, the electrical resistance of the material generates heat. This phenomenon is known as Joule heating or resistive heating. The amount of heat generated is proportional to the square of the current (I^2) and the resistance (R) in the material, according to the formula H = I^2 * R, where H is the heat generated.

Example 2: Chemical Reactions

Some chemical reactions that take place within a solid material can produce heat. A common example is exothermic reactions, where heat is released as a byproduct during the reaction. For instance, concrete generates heat during the curing process when cement reacts with water, which can lead to an increase in temperature within the material.

Example 3: Nuclear Decay

Heat is generated in solid radioactive materials due to the decay of their radioactive isotopes. As these isotopes decay, they release high-energy particles and radiation, which impart energy to the neighboring atoms and generate heat. For example, the decay of uranium or plutonium in nuclear fuel rods generates heat, which is then converted to steam and used to produce electricity in nuclear power plants.

Example 4: Frictional Heating

When two solid surfaces come into contact and slide against each other, friction is generated, which can produce heat. This phenomenon is known as frictional heating, and it occurs due to the mechanical work done against the opposing force of friction being converted into thermal energy. Examples include the heat generated by brakes in vehicles, and the heat produced when gears mesh together in a gearbox or when a drill bit is used to bore into solid materials.