What is joule law?

Answer 1

Joule's laws are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively. Joule's first law, also known as the Joule effect, is a physical law expressing the relationship between the heat generated by the current flowing through a conductor. It is named for James Prescott Joule who studied the phenomenon in the 1840s. It is expressed as: : Where Q is the heat generated by a constant current I flowing through a conductor of electrical resistance R, for a time t. When current, resistance and time are expressed in amperes, ohms, and seconds respectively, the unit of Q is the joule. Joule's first law is sometimes called the Joule-Lenz law since it was later independently discovered by Heinrich Lenz. The heating effect of conductors carrying currents is known as Joule heating. Joule's second law states that the internal energy of an ideal gas is independent of its volume and pressure, depending only on its temperature.

Answer 2

There are two joule's laws. The first shows how much heat is generated by a current flowing through a conductor. The second states that a gas's internal energy does not change with volume or pressure, but with temperature.

Answer 3

joules law state that , the heat generated in the conductor by the flow of electric current is proportional to the square of electric current value, the resistance value of the conductor & time taken to the flow of current.

Answer 4

Joule's Law describes the heat produced by a resistor in terms of the resistance and the current:

P = I2R

where P is the rate of heat production in watts, I is the current through the resistor in amperes, and R is the resistance of the resistor in ohms.

Alternate representations make use of Ohm's Law (V=IR):

P = VI = V2/R

where V is the voltage across the resistor.

The total heat energy produced by a resistor is found by integrating the equation with respect to time. For a constant current and resistance this is simply:

Q = I2Rt = VIt = V2t/R

where Q is the energy in Joules, and t is the time duration in seconds.

For example: A toaster has a 10-ohm resistance, connected to 120 volts. By Ohm's Law, it will draw a current of 12 amperes. By Joule's Law, it will emit heat at a rate of 1440 watts. If left on for 60 seconds it will produce 86,400 joules of heat energy. (Note that in a real toaster, the resistance of the heating element is not constant; it varies widely with the temperature).