A rectangular coil that forms the rotor of a simple d.c
PHYSICS · Multi-part · GCSE · Physics · Magnetism and Electromagnetism · Magnetism and Electromagnetism
Problem
A rectangular coil that forms the rotor of a simple d.c. motor consists of 500 turns, each of length 8.0cm and width 6.0cm. It carries a current of 3.0A and rotates in a uniform radial magnetic field of flux density 0.80T.
(i) Derive an expression for the mechanical work done by the magnetic forces on the coil in one complete revolution, assuming the torque remains constant in magnitude throughout the rotation.
(ii) Using the given data, calculate the work done per revolution.
(iii) If the motor runs at a steady speed of 50rev s−1, determine the mechanical power output.
(iv) Qualitatively explain how the mechanical power output would change if the current through the coil were doubled while all other factors remain unchanged.