The armature in a motor rotates due to the presence of a _______ field.

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Solution

Magnetic Field
An electric motor is a machine that converts electrical energy into mechanical energy. When current flows through a conductor a magnetic flux is generated around the conductor. A magnetic flux also exists between north and south poles of a permanent magnet. When these two fluxes are allowed to interact, that is the current-carrying coil called armature is placed in a magnetic field.

The armature would react in the same way that another magnet would. This result in the rotation of the armature.

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Similar questions

Q. The armature of a DC motor is rotating in the clockwise direction as shown. What is the direction of the magnetic field for the given motor?

Commercial electric motors do not use a permanent magnet to rotate the armature.

Q. An 8 kW, 230 V, 1200 rpm dc shunt motor has armature resistance as

0.7 Ω

. The field current is adjusted until on no load with a supply voltage of 250 V, the motor runs at 1250 rpm and draws armature current of 1.6 A. A load torque is then applied to the motor shaft, which causes the armature current to rise to 40 A and the speed fall to 1150 rpm. The reduction in flux per pole due to the armature reaction is____%

Q. An 8 kW, 250 V, 1200 rpm dc shunt motor has

R_{a} = 0.7 Ω

. The field current is adjusted, until on no-load with a supply of 250 V, the motor runs at 1250 rpm and draws armature current of 1.6 A. A load torque is then applied to the motor shaft, which causes the

I_{a}

to rise to 40 A and the speed falls to 1150 rpm. The reduction in flux per pole due to armature reaction is___________%.

Question 6
Commercial electric motors do not use

(a) an electromagnet to rotate the armature
(b) effectively large number of turns of conducting wire in the current carrying coil
(c) a permanent magnet to rotate the armature
(d) a soft iron core on which the coil is wound

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