magnetism - the electric motor

Question 1

the electric motor effect

Answer 1

• current running in opposite directions on either side of loop
• when placed in magnetic field, wire experiences a force on both left and right sides (use left hand rule to figure out with direction the force is)
  -now we have a moment on both left and right hand side
• means loop will rotate in clockwise direction

Question 2

what is the problem when the loop rotates to 90 degrees?

Answer 2

• it will stop rotating
• if it goes beyond, the direction of the current means the force on the left hand side is acting downwards and force on right hand side acting upwards. these forces push it back to 90 degrees position

Question 3

how to solve problem of loop stopping rotating at 90 degrees?

Answer 3

switch direction of the current when loop passes 90 degrees. we use a device called spit-ring commutator. it is a split metal ring which is connected to conducting brushes which allow the electric current to pass onto the ring.current now produced a turning effect on motor. force causes motor to rotate in clockwise direction. current is broken for a tiny fraction of a second, however wire keeps turning due to momentum and current switches direction. so force on left hand side still acts upwards and force on right acts down

Question 4

by switching the direction of the current, the split ring commutator allows…..

Answer 4

the motor to keep rotating in the same direction