Voltage, Current, Resistance Concepts

Voltage unit is Volt, Current unit is Ampere and Resistance unit is Ohm.
In the example circuit, the total resistance of the circuit is RT = R1 + R2 + R3 Ohms.
When switch A is closed; a current I flows. This current is found by dividing the supply voltage of the circuit by the total resistance of the circuit.
I = V/RT Amps.
This current passing through the circuit creates a voltage when passing over the resistors as seen in the picture.
v1 is the voltage/voltage deployed above R1.  v1= I x R1.
v2 is the voltage/voltage deployed above R2.  v2= I x R2
v3 is the voltage/voltage deployed above R3.  v3=  I x R3