ICSE Class 10 Answered

please explain woring of ac ,dc motor . explain even coil rotation and current direction

Asked by Badrinadh | 27 Aug, 2018, 05:06: PM

Expert Answer

AC generator:

An AC generator is a device which converts mechanical energy into electrical energy using the principle of electromagnetic induction.

- Slip rings provide a means for connecting the rotating armature of a simple a.c. generator to an external circuit.

- As the armature naturally produces an alternating voltage, an alternating voltages appears across the slip rings.

- There are two coaxial metallic rings R₁ and R₂.

- They rotate along with the coil. One end of the coil is connected to the slip ring R₁, and the other end of the coil is connected to the slip ring R₂.

- Each ring slips against the brush which is stationary.

- Two carbon brushes B₁ and B₂ press gently against the slip rings R₁ and R₂, respectively.

- The other ends of brushes act as terminals of the generator for the external circuit.

- The external circuit (i.e. load) is connected between the other ends of brushes.

- The brushes B₁ and B₂ do not rotate along with the coil and the slip rings.

DC motor:

An electric motor is a device which converts electrical energy into mechanical energy.

- To obtain a d.c. voltage, it is necessary to reverse the direction of the natural alternating voltage every half cycle, producing full wave rectification.

- This is achieved using a split-ring commutator which, essentially, is a rotating switch.

- Whenever the coil passes from the vertical position, the direction of current through the coil has to be reversed so that the coil continues to rotate in the same direction.

- Hence, the two parts S₁ and S₂ of the split ring are used to act as a commutator to reverse the direction of current in the coil, so they are called the split ring commutator.
- So, slip rings are used with simple a.c. generators, whereas a commutator is used with d.c. motors.

Answered by Abhijeet Mishra | 28 Aug, 2018, 01:00: PM