In 1919, the 18th Amendment to the U.S. Constitution, which prohibited the sale and manufacture of alcohol, was ratified. It went into effect on January 16, 1920âbeginning the era known as Prohibition.
Because time constant calculations are important, and often needed, it is better to make the definition of the time constant (T) in a CR circuit: THE TIME TAKEN FOR THE VOLTAGE ACROSS A CAPACITOR TO INCREASE BY 63.2% OF THE DIFFERENCE BETWEEN ITS PRESENT AND FINAL VALUES.
But, for an LR circuit, the answer comes from studying the solution of the differential equation for the circuit. The solution is exponential in nature, and the time constant is a measure of the decay rate. Basically, time constants fall out of first order differential equations.