Is there something about 9V batteries that I don't know about? (1 Viewer)

[EpaX]

So I've built this DC motor for my Physics assignment. It runs perfectly fine on a 6V battery pack and 3V battery pack but doesnt seem to work on a 9V rectangular battery (with battery snap); well, the coil moves slightly so it seems that there's minimal current going through the coil. However, the RPM is quite decent at 3V so I don't see why a 9V battery can't provide the current that a 3V battery can to run the motor. And no, the battery isn't dead. Everything else like the connecting wires are fine too, and I even tried with different 9V battery. Any ideas on why a 9V battery doesn't work?

 

[anomalousdecay]

There are many possibilities for this.

Could be over heating of the coil or too much current or the current is short circuiting between the sides of the coil so it just goes from one side to another along the shortest path so not enough moment of inertia (or informally the rotational/torque inertia) occurs.

Its hard to tell without actually looking at what is happening myself and taking measurements through the coils.

 

[Parvee]

There are many possibilities for this.

Could be over heating of the coil or too much current or the current is short circuiting between the sides of the coil so it just goes from one side to another along the shortest path so not enough moment of inertia (or informally the rotational/torque inertia) occurs.

Its hard to tell without actually looking at what is happening myself and taking measurements through the coils.

Source: EE

 

[anomalousdecay]

Source: EE

Nah I had to cross reference this with a friend too. So EEs

But yeah if you had an insulated wire and used a charged up capacitor (note these are not batteries) then you could fix the problem. However, its more trouble to do that than its worth. Just use that 3V or 6V or whatever works best for you.

 

[EpaX]

Could be over heating of the coil or too much current or the current is short circuiting between the sides of the coil so it just goes from one side to another along the shortest path so not enough moment of inertia (or informally the rotational/torque inertia) occurs.

I connected a 3V battery pack to a 6V battery pack in series and the motor runs just fine, with decent RPM; + the coil doesn't feel warm so i don't think overheating or too much current is the problem. Also, the coil is enameled so it shouldn't be short circuiting. :/

 

[anomalousdecay]

I connected a 3V battery pack to a 6V battery pack in series and the motor runs just fine, with decent RPM; + the coil doesn't feel warm so i don't think overheating or too much current is the problem. Also, the coil is enameled so it shouldn't be short circuiting. :/

Assuming you connected them the right way, then you might have 9V. However, this might have something to do with an internal battery resistance. This usually means the battery is dead.

However you said it wasn't dead, so I think what you could be doing is maybe reverse biasing the batteries when connecting them in series.

You have to connect the positive of one to the negative of the other to forward bias them.