# Effect of a pair of slip rings in a DC motor

1. Jun 3, 2009

### Starbright

Effect of a pair of slip rings in a DC motor

Hi, I have a question here.

Knowingly that the effect of a slip ring in a DC motor is to reverse the direction of the current in a loop whenever the commutator changes contact from 1 brush to another, so as to ensure the loop to be always rotating in 1 direction.

However, what will be the effect if the slip ring is substituted by a pair of slip rings then?

2. Jun 4, 2009

### Staff: Mentor

Welcome to the PF. What are your thoughts on this question? Hint -- if you have one slip ring, what happens if the motor comes to rest with the brush directly over the gap?

3. Jun 4, 2009

### Starbright

For a single slip-ring DC motor, the momentum of the loop will carry it past the vertical position. This reverses the current and the loop, due to the force generated, will continue to rotate in the same direction.

But I am not sure what happens if there is an additional slip ring installed.
Appreciate if you can explain to me what will happen then.
Thanks.

4. Jun 4, 2009

### Staff: Mentor

What do you think about my hint?

5. Jun 4, 2009

### Starbright

I still don't understand the concept and appreciate if you can explain to me in details, if there are 2 slip rings instead of one, in a DC motor.

6. Jun 4, 2009

### Staff: Mentor

I can't give you the answer to your homework question. Try reading through this article -- it should help you figure out the question:

http://en.wikipedia.org/wiki/Brushed_DC_electric_motor

.

7. Jun 5, 2009

### Andrew Mason

I think a slip ring provides simply a continuous circular contact. They aren't used in a DC motor. I think the question asks for the effect if you were to use them in a DC motor (instead of a commutator).

AM

8. Jun 5, 2009

### Staff: Mentor

Ah, interesting. I see now that "slip ring" and "commutator" do not go together:

http://en.wikipedia.org/wiki/Slip_ring

Thanks for that. Still, the OP kind of mixes the terms, so now I'm not sure what the question really means...