[Music] hi welcome back to three sighs lessons Cole you K by the end of this video you should be able to describe how an electric motor works and this is for higher-tier students only in the last video we saw that when a conductor such as a wire is carrying a current it experiences a force in a magnetic field scientists call this the motor effect remember that we can determine the direction of the force by using Fleming's left hand rule now there is one really useful application of the motor effect and that is an electric motors I'm showing you here a loop of wire carrying a current and we can see that the current is running in opposite directions on either side of the loop on the left hand side the currents running back to front but on the right hand side the currents running front to back we've now placed a loop of wire in a magnetic field now the wire experiences a force on both the left and right sides like this using Fleming's left hand rule we can see that the force on the left hand side acts upwards and the force on the right hand side acts downwards so now we've got a moment on the left hand side and a moment on the right hand side this means that the loop will rotate in the clockwise direction like this however there was a problem here once the loops at 90 degrees it will stop rotating imagine that the loop rotates beyond 90 degrees now the direction of the current means that the force on the left hand side is acting downwards and the force on the right hand side is acting upwards so these forces push the loop back to the 90 degrees position however we can solve this problem if we switch the direction of the current when the loop passes 90 degrees to do that we use a device called a split ring commutator and I'm shown that here the split ring commutator is a split metal ring this is connected to conducting brushes the brushes allow the electric current to pass onto the ring so this shows the Kohen producing a turning force on the motor the force makes the motor rotate in the clockwise direction at this point the currents and for a tiny fraction of a second however the wire keeps turning due to momentum now the current switches direction so once again the force on the left-hand side still acts upwards and the force on the right-hand side still acts downwards so as you can see by switching the direction of the current the split limb commutator allows the motor to keep rotating in the same direction remember you're fine plenty of questions on the electric motor in my vision workbook and you can get up by clicking on the link above [Music]