Identify problems with experiment question... (1 Viewer)

[Komaticom]

Does the coil even touch the brushes?
I said a cylindrical block of solid touch both brushes, and the coil aren't connected to the brush, so no current will flow, and therefore there will be no force/torque/current.

I avoided the risk of saying forces acting on the coils because that implies that a current will flow, which I wrote, it didn't.

 

[helper]

School demonstration generators use brass or copper for the brushes. So if you explain they might give it but just saying it they probably won't

 

[Komaticom]

I clearly recall that the coils are wound around the area in the magnetic field, and there is no visible contact with the brushes. The coil is wound pathetically around that rectangular block of some unknown material, and that rectangular block is attached to a cyclindrical block of some unkown material. It is this cylindrical block that touches the brushes, both of them, so I don't think current would flow very well if the coils don't touch the brushes.

Graphite has a lubricating property. Copper doesn't.

 

[helper]

There is no point arguing over it now. Yes graphite is better for the brushes but copper is acceptable and used for a lot of demonstration appliances. This a student model and copper is acceptable.
It is the copper split ring commutator that touches the brushes.
The wires however don't join to the commutator.

 

[Komaticom]

Argh. My photographic memory is wavering...

There was a commutator, but the coils are only wound around the rectangular block... so no current.

I asked this before, but I'll ask again:
Did anyone mention the pins as a fault?

 

[helper]

Then pins would only be fault if there isn't free level rotation.

 

[Brad]

1. The plane of the coil was perpendicular to the direction of magnetic field so torque would be 0 because cos90 = 0

2. coils not in contact with commutator

3. no power source"


thats what i put.....