What is armature voltage?

Hint: An armature is a rectangular coil having a large no. of turns of conducting wire over an iron core and armature voltage is a voltage developed across the terminal of the armature. The armature is used in both AC and DC devices like generators where it carries current across the field and interacts with the magnetic field to generate power.
Formula used:
The armature voltage can be calculated as
\[V = k\eta \phi \]
Where \[V = \] armature voltage
\[K = \] constant depends on the armature
\[\eta = \] speed of armature
\[\phi = \] magnetic flux

Complete answer:
An armature is a rectangular coil which has large no. of turns of copper wire over a soft iron core, it is used in both AC and DC machines like generators and motors. When the slip rings that are connected to armature starts to rotate because of the magnetic field as in a motor or by mechanical means in the generator the armature move because of magnetic field and thus by which there is induced current in it, the current induced here is by the potential difference which is developed in the terminals of the armature during power generation.
Therefore, the armature voltage is
\[V = k\eta \phi \]
Where \[V = \] armature voltage
\[K = \] constant depend on the armature
\[\eta = \] speed of armature
\[\phi = \] magnetic flux

Note:
The armature voltage can be varied by voltage control method. In this method, the shunt field is connected to a constant exciting voltage, and the armature is supplied with different voltages. The voltage across the armature is varied with the presence of suitable switchgear. The speed is nearly proportional to the voltage across the armature.
Generally, the typical armature voltage ratings in the US are \[90,180,240,\] or \[500\] VDC. The ratings of general U.S. field voltage are \[100,200,150,\] or \[300\] VDC. As stated previously, the value of applied voltage to the armature dictates the output shaft speed.