Circuits Ohm s law

Using Ohm s law the unit of voltage, called the volt (V), can be defined by the two precedent units as the potential difference required for a flow of current of one ampere through a conductor having a resistance of one ohm. In a closed electric circuit wo can write the equation E — IR, E meaning the electromotive force of the source of current connected to the circuit. Ohm s law can also be applied, however, to a part of an electric circuit then E = IR stands for the voltage or potential difference across the givon part of the conductor. 

It is important to understand that Ohm s law is not a fundamental law that always applies, such as the law of gravity. Rather it is an empirical law that has been found by experiment to work fairly well most of the time. There are times, however, usually in extreme cases, when Ohm s law breaks down. For example, if an extremely high voltage is applied across a circuit. Ohm s law will not predict the correct value for the current. Even though Ohm s law does not always apply it works for most everyday situations and is therefore very useful. 

If an engineer knows two of the measurements of an electrical circuit, Ohm s law allows the missing value to be calculated. 

Note that the extent to which the voltage lags the current in an RC circuit, , depends on the frequency /, the resistance R. and the capacitance C, of the circuit. Ohm s law for a series RC circuit can be written as... 

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