Question 1: Explain with diagram sinusoidal alternating voltage and sinusoidal alternating current.
When the variation of a physical quantity with time occurs between two points, the graph of variation of the quantity with time is like a wave. Since the sine values also change between +1 and -1, therefore, the graph of sine values is also like a wave. Such a wave is called a sinusoidal wave.
An alternating voltage is produced by rotating a coil with a constant angular velocity ω, in a uniform magnetic field. As the coil rotates continuously with the same angular velocity, it changes its direction continuously, the polarity of the alternating voltage also changes over time. When the graph of such a voltage is taken with time, it takes the form of a sine wave, representing the sinusoidal alternating voltage. Mathematical form of the graph is
Here V = instantaneous voltage, Vm = peak or maximum voltage
ω = angular velocity, and t = time
In an electric circuit, the alternating voltage is shown by
The current which changes its direction many times in a second is called a sinusoidal current.
Sinusoidal current is generated by a A.C generator which produces alternating voltage.
Value of the sinusoidal current at any instant is given by
Here I is the instantaneous current, Im is the maximum current and ω is the angular velocity of the current.