- #1
grade11studentgoaat
- 8
- 5
- Homework Statement
- i thought i made it perfect
- Relevant Equations
- none
Why doesn’t my electric motor work?
- Thread starter grade11studentgoaat
- Start date
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The electric motor is likely not functioning due to a metallic axle that may be shorting the copper wires connected to the rotor and battery. The rotor has insufficient turns, with hundreds of turns recommended for better performance. Additionally, the rotor lacks a ferromagnetic core, which is essential for concentrating magnetic flux and enhancing motor operation. The internal resistance of the 6-volt lantern batteries is about 1 ohm, causing significant voltage drop when the motor runs, and using smaller diameter wire with more turns is advised. A 9-volt battery is also unsuitable due to its higher internal resistance, further impacting performance.
- #2
marcusl
Science Advisor
- 2,963
- 671
Based on your photo, a few observations are possible. First, your axle is metallic, likely shorting out the copper wires leading to your rotor as well as the wires from the battery. Second, your rotor seems to have very few turns. I would expect to see hundreds (or more!). Third, you do not appear to have wound your rotor windings around a ferromagnetic core, such as a steel bolt, that would concentrate magnetic flux and improve chances of operation. It would also give you a flywheel action that would tend to keep the motor spinning once it was started. You can provide us with additional information as we proceed.
- #3
grade11studentgoaat
- 8
- 5
i will try out what you said. thank you for your feedback!!!
Last edited by a moderator:
- #4
jrmichler
Mentor
- 2,432
- 3,489
Also, those 6 volt lantern batteries have internal resistance about 1 ohm. The small amount of wire in the winding has very low resistance, so the battery voltage will drop to near zero when running this motor. Try using smaller diameter wire, say about 30 gauge, and at least 100 turns in each pole winding. More turns would be even better. And that 9 volt battery on your table is even worse because the internal resistance is much higher.
The answer is (B) but I don't really understand why.
Based on formula of Young Modulus:
$$x=\frac{FL}{AE}$$
The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A##
I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...
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