This causes continual rotation of the loop. By the time the loop flips over, current flows through the wires again but now in the opposite direction, and the process repeats as in part (a). No torque acts on the loop, but the loop continues to spin from the initial velocity given to it in part (a). (b) The brushes now touch the commutator segments so that no current flows through the loop. Therefore, the loop has a net torque and rotates to the position shown in (b). The forces on the wires closest to the magnetic poles (N and S) are opposite in direction as determined by the right-hand rule-1. (a) The rectangular wire loop is placed in a magnetic field. The brushes press against the commutator, creating electrical contact between parts of the commutator during the spinning motion.įigure 11.15 A simplified version of a dc electric motor. ![]() A basic commutator has three contact areas to avoid and dead spots where the loop would have zero instantaneous torque at that point. The commutator is set to reverse the current flow at set points to keep continual motion in the motor. This reversal of the current is done with commutators and brushes. Once the loop’s surface area is aligned with the magnetic field, the direction of current is reversed, so there is a continual torque on the loop ( Figure 11.15). Electrical energy is converted into mechanical work in the process. When current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft. Motors contain loops of wire in a magnetic field. Motors are the most common application of magnetic force on current-carrying wires. Define the magnetic dipole moment of a current loop. ![]()
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