Creating A Motor
Jamie Ma, Morgan Poon
Burnaby South Secondary
Floor Location : J 163 N
Round and round it goes, when will it stop, only science knows. For our project, we investigated the relationship between the number of turns in a coil and the RPM induced in the coil, by a fixed magnet. Our hypothesis was if we increase the number of turns in a coil, then the RPM will increase, provided the current remains constant.
To do this, we needed to design an experiment that could test the strength of the magnetic field of the neodymium magnet in relation to the magnetic coil. We made a simple motor that works by letting an electrical current run through the bare side of the coil and out the other side, then shutting off once the insulated side rotates and comes into contact with the stands. Then the magnet pushes and pulls the coil in quick succession and makes it rotate.
Unfortunately, there are many variables we needed to control to make a final and accurate reading of the RPM. To find and neutralize these variables, we needed the help of two laws, Ampere’s Law and Ohm’s Law. Ampere’s law helps us by stating, if the current remains constant, and the number of turns increases, then the magnetic field will be stronger and the RPM will increase. Ohm’s law helps us by stating that if we want the current to remain constant, then we must increase the voltage as the resistance increases. This helps us by giving us a way to balance out both laws by applying them together and making the testing accurate.
For our experiment, the independent variable is the number of turns and the dependent variable is the induced RPM. In our control experiment, we used a coil with no turns. We created 8 magnetic coils, each with a different amount of turns, increasing by 3 from 0 to 21. For each coil, we adjusted the voltage to the correct amount, using Ohm’s law, so the current would remain constant as the resistance increases. We tested the RPM of each coil by creating a motor and using a Photo Tachometer to measure the RPM.
Our results show that the average RPM increases as the number of turns increases. Our results were affected by uncontrolled events such as the imperfections in the construction of the coils. We tried to mitigate these imperfections by using the erasers and the metal clips to minimize the horizontal and vertical fluctuations of the spinning coils.
A possible source of error is the additional weight of the coils as we added more turns. The induced RPM peaks at the 18 turn coil but the RPM decreases at the 21 turn coil which is likely due to the added weight of the number of turns. We tried to reduce the weight difference between the coils by using a lighter weight wire and minimizing the number of turns. We can conclude that our results support our hypothesis and the RPM does increase as the number of turns increases.