Voltage induced in a DC generator is AC or DC?

Q " Voltage induced in a DC generator is AC or DC?

 Hello Friends . We very well know that the machine which converts the mechanical energy into an DC electrical current is called as the electric generator. 

It is quite interesting , the induced voltage in the armature winding of a DC generator is not DC but it is AC .

Let us see how this is possible . To understand this concept we have to overlook the working principle of the DC generator .

Working principle:

When a conductor is moved through a magnetic field an e.m.f. is induced between its ends. 

Let the length of the conductor be 'L' m and the flux density of the field be B N/m^2 (refer above figure).

If the conductor moves with velocity 'v' (m/sec ^2 )at right angles to the field, then the flux cut per second will be BvL (since the conductor will sweep out an area vL every second).

But the rate of change of flux is equal to the e.m.f. induced in the conductor. Therefore,

E = BLv

If the conductor cuts through the flux at an angle θ( θ is the angle between the magnetic field and the direction of motion),

 the equation becomes,

E = BLv sin θ 

Hence ,if B,l and v are constant then  

E= k sinø 

Hence , E is directly proportional to sinø. Therefore ,shape of emf will be a sine wave . The induced voltage is maximum at ø= 90° and 270° and minimum at ø= 0° ,180° and 360° . One rotation of the armature conductor corresponds to one cycle of induced emf .

Thus it is interesting to note that, the induced voltage in the armature winding of a DC generator is not DC but it is alternating. 

To convert it into a unidirectional (DC) signal , we have to use a rectifying device called commutator. Thus it is a device used in the DC generators to convert alternating induced voltage to a DC voltage . 

I hope this helps you. Thank you ❤️.