In DC motor

• In DC motor the classification is done according to the connection of the field winding to the armature.
• In a DC motor, the armature resistance is typically very low, usually less than 1 Ω, and sometimes even between 0.1 Ω and 1.5 Ω
• A DC generator is an electrical machine whose main function is to convert mechanical energy into electricity. When the conductor cuts magnetic flux, an emf will be generated based on the electromagnetic induction principle of Faraday’s Laws. This electromotive force can cause a flow of current when the conductor circuit is closed.

• The emf equation of the DC generator is given by the equation:

\({E_b} = \frac{{PNϕ Z}}{{60A}}\)

where

Z = Total number of armature conductor

P = The number of poles in a generator

A = The number of parallel paths

N = Speed of armature in r.p.m

ϕ = Flux per pole

Lap winding 

A = P

Wave winding

A = 2

• back e.m.f. depend on the number of poles
• back e.m.f. is is directly proportional to the speed of rotor