What is Joule's Heating?
Joule heating, also known as Joule's law, is the process by which resistance in a circuit transforms electric energy into heat energy. In 1840, the English physicist James Prescott Joule discovered that the amount of heat generated per second in a wire carrying a current is proportional to the electrical resistance of the wire and the square of the current. He calculated that the heat evolved per second equals the electric power absorbed, or power loss.
- The heat evolved per second, or the electric power loss, P, is defined quantitatively as the current I squared times the resistance R, or P = I2R.
- When the current is expressed in amperes and the resistance in ohms, the power P is measured in watts or joules per second.
Joule First Law of Heat
The first law of joule shows the relationship between heat produced by flowing electric current through a conductor.
- When the current in the circuit and the flow of current remain constant, the amount of heat generated is proportional to the electrical resistance of the wire.
- When the electrical resistance and current supply are constant, the amount of heat generated in a conductor carrying current is proportional to the square of the current flow through the circuit.
- When the resistance and current flow are held constant, the amount of heat produced by the current flow is proportional to the time of flow.
Formula:
Q = I2 R T
- Where Q represents the amount of heat and I represents electric current
- R denotes the conductor's electric resistance.
- T stands for time.
Second Law of Thermodynamics
According to Joule's second law, the internal energy of an ideal gas is independent of volume and pressure, and only depends on temperature. Magnetostriction is a ferromagnetic material property that causes it to change shape when exposed to a magnetic field.
- It also states that the internal energy of an ideal gas is independent of volume and pressure and only depends on temperature. T = 1 for an ideal gas defined by appropriate microscopic postulates, implying that the temperature change of such an ideal gas during a Joule-Thomson expansion is zero.
Applications of Joule's Law
- The heating effect of current is used in the operation of electric heating appliances such as an iron, oven, room warmers, geysers, and so on.
- The warming effect of alternating current is used by electric bulbs.
- The heating effect of an electric fuse is used to protect residential wiring and electrical devices.
- The heating action of electric current was used during the laundry ironing process.
Joule'sLaw: Salient Points
- Joule's law in electricity is a mathematical explanation of how quickly resistance in a circuit converts electric energy to heat energy.
- Mr. James Prescott Joule calculated that the heat emitted every second equals the absorbed electric power, also known as power loss.
- The joule's first law demonstrates the relationship between heat generated by passing an electric current through a conductor. Q=I2RT
- The mechanical equivalent of heat is the amount of work required to produce one unit of heat on a system.
- The mechanical equivalent of heat is the number of units of work required to produce a unit quantity of heat on a system.
- The amount of work done on the system and the amount of heat produced by it determine the mechanical equivalent of heat.