ELECTRICITY & MAGNETISM

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Joule's laws

1. The rate of heat production by a steady current in any part of an electrical circuit is proportional to the resistance and to the square of the current. In other words, the heat (Q) produced when an electric current (I) flows through a resistance (R) for a time (t) is given by Q = I ²Rt.


2. The internal energy of a given mass of gas is independent of its volume and pressure, being a function of temperature alone. This law applies only to ideal gases (for which it provides a definition of thermodynamic temperature) because in a real gas intermolecular forces would cause changes in the internal energy should a change of volume occur.

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