decrease the speed of rotation of armature coils?
Answers
(i) The strength of the magnetic field.
(ii) The current in the coil.
Answer:
When a current flows through the armature coil, forces act on it as a result of its current carrying conductors being in the magnetic field provided by the permanent magnet and so cause the armature coil to rotate. For a coil rotating in a magnetic field, a voltage is induced in it in such a direction as to oppose the change producing it and so there is a back e.m.f. Thus, the electrical circuit we can use to describe the motor has two sources of e.m.f., that applied to produce the armature current and the back e.m.f. The electrical circuit model is thus as shown in Figure 8.16. Just two elements, an inductor and a resistor, are used to represent the armature coil. The equation is thus:
hope this helps you mate xD