Magnetism Day 3 Magnetic Forces on CurrentCarrying wires

RHR-1 PRACTICE Sign + Magnetic Field East Velocity North Force Sign Magnetic Field Down

When current flows through a wire, the individual charges are forced in a certain

THE DC MOTOR Split-Ring Commutator (SRC) Field Magnets (Permanent Magnets) Brushes Current Source Loop

The purpose of each part Source: Provides current to the loop. Loop: Provides a

The picture below shows a crosssection of the wire loop (showing a cut at

Find the direction of the force on the loop of wire at point ….

Some practice problems Which direction will the orange dot move? N S I I

What would happen if …. #1) The loop of wire was perpendicular to the

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Magnetism Day 3 Magnetic Forces on Current-Carrying wires

RHR-1 PRACTICE Sign + Magnetic Field East Velocity North Force Sign Magnetic Field Down Velocity West Force South Sign - Sign + Magnetic Field North Magnetic Field East Velocity West Velocity Force West Force

When current flows through a wire, the individual charges are forced in a certain direction, and thus the wire experiences a force. Wire of length L Since d = rt, L = v. Dt Fmag I Remember, I consists of + charges.

THE DC MOTOR Split-Ring Commutator (SRC) Field Magnets (Permanent Magnets) Brushes Current Source Loop of currentcarrying wire http: //www. walter-fendt. de/ph 14 e/electricmotor. htm

The purpose of each part Source: Provides current to the loop. Loop: Provides a path for the current to flow, and feels the FORCE that turns the motor. Split-Ring Commutator (SRC): Allows current to flow into the loop and out of the loop. Switches POLARITY every 180 o (or half-turn) Brushes: Keep in contact with the SRC (which is turning) without causing the wires to the source to get wound up, kinked, or coiled. Field Magnets: Create a B field that forces the wire to turn.

DC Motors: How they work

The picture below shows a crosssection of the wire loop (showing a cut at the location of the pink dashed line).

Find the direction of the force on the loop of wire at point …. A B C D When does the wire loop experience …. #1) Maximum Force? #2) Zero Force? What major event happens every half-turn? C D

Some practice problems Which direction will the orange dot move? N S I I Which direction is current flowing? Into A or out of A? N S A A

What would happen if …. #1) The loop of wire was perpendicular to the B-field when the battery was hooked up? #2) The magnets were removed from a DC Motor? #3) The Split-Ring Commutator wasn’t split, but was a solid ring? #4) The wire loop had many LOOPS (WINDINGS) before coming back to the commutator? #5) The current was AC (Alternating Current) instead of DC (Direct Current) #6) The brushes hit the “split” in the split-ring commutator?