Question

(2) In the second demonstration involving an extremely simple, but subtle, DC motor, here is a picture: r that the the two copper posts on each side are conducting electricity from a D size battery below, inside the red container. Each wire on the left and right is supported by a copper post. The wire had an electrical insulating enamal around it, but I shaved the enamel off on half of the wire to the left, and to the right. I explained what did here in class. Explain how this device works. Please draw a diagram and integate things like magnetic field and changing magnetic field If you increase the number of windings of the copper wire, does this help? . If you flip the magnet, as we demonstrated, the "motor" changes direction. Why? A diagram would be helpful here How might you make it go faster? What happens if, say, on the left side, I had shaved all the enamel off, but kept the half shaved enamel off on the right side. I did not demonstrate this. Think about it.

Answer 1

A)

A DC motor such as this works on three principles:

1. Current going through a loop can produce a magnetic field
2. opposite pole attracts, same pole repels.
3. Objects on the move don't stop unless some force from outside stops it. This is called inertia.

As the copper posts carry electricity and also support the coil to move freely on a fixed axis and carry current through it. At start when the coil is electrified and produces its own magnetic field, it interacts with the magnet and gets repelled, this cause a half rotation of the coil to a more stable position, the half shaven enamel works as an automatic switch to cut off the electricity once the coil has aligned itself so that it doesn't get repelled any more.

Now as this half rotation happens very fast and there's no electricity on the coil so inertia comes into play and rotated the coil further to the initial position and current turns on again and the whole cycle just repeats. The rotation of the coil continues and motion becomes perpetual.

B)

Increasing the number of turns will definitely help the motor to speed up to an extent, because the magnetic field generated by the coil is proportional to its turn, and that field determines how quickly the coil turns by repelling the magnet, but too much turn will make the coil heavy and cause a restriction of motion.

C)

As the scrapped off enamel stays the same but the magnet's pole is now flipped the "stable" point on the horizontal line flips to the other side. i.e. say if it was on the left of the axis, after flipping the magnet it goes to the right. And naturally the coil wants to go that opposite way in the initial half rotation. And the whole rotation gets flipped.

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D)

increasing the input voltage will result more intense field on the coil and it will rotate faster. And increasing the turn in the coil will also result more intense field and faster rotation, but too much turn will make the coil heavy and decrease the speed so caution should be taken while designing the coil for the optimum speed.

E)

As there is still a little bit of enamel left on the right spot, so the coil will still turn off at the right position and motion will happen without any alteration.