# What is voltage Source?

A device which produces a voltage output continuously is known as a voltage source. There are two types of voltage source one is direct voltage source and other is an alternating voltage source.

# Direct voltage source:-

A device that produces a voltage output continuously is called a direct voltage source.General examples of direct voltage sources are batteries and d.c generators. Direct voltage source always maintains the same polarity of the output voltage Which means when the load is connected across the source current flows from positive to negative terminal of the voltage source. This is known as direct current. Direct current flows in one direction. The load current inside the direct voltage source is known as internal resistance Ri. As shown in the above figure internal emf is generated denoted by Eg in series with the internal resistance Ri

Terminal Voltage, V= (E– I Ri) or IRL

# Alternating Voltage Source:-

A Device that produces alternating voltage output continuously is known as the alternating voltage source. Example of an alternating voltage source is the a.c generator. Alternating voltage produces periodically reverse output voltage. Therefore polarity is reversed. When the load impendence is connected across the alternating voltage source current flows in the circuit that periodically reverses in direction, Which called alternating current. The opposition to the current is called internal impedance, denoted by zi. The e.m.f is generated in series with the internal impedance is denoted by Zi.

Load current, I = Eg /ZL+Zi

Terminal Voltage,V=(Eg-I Zi) or IZL