# Homework Help: Torque of an electric motor?

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1. Oct 29, 2015

### Physics GOD

Can someone tell me if the parts of what i've done are right, and explain the questions i've missed. We have just done a lab on split-ring commutators and i'm currently doing a lab report.

"Explain what is meant by the torque of an electric motor. Use a diagram"

I've said that 'The torque of an electric motor is the force that will carry the armature to the other side where it will make contact with the other magnet which will give it force to spin through and continually repeat.' Is this right? What can I add? and i'm really confused on where it says "Use a diagram" What diagram do I use?

"Name three ways this torque could be increased."
I've said '1) Increase the current flowing.' I dont know what are two more ways apart from maybe voltage or strength of the magnets?

Lastly, as the experiment was going on there were some sparks. Why is this? Is this from the metal on metal contact and is it similar to what may happen in a car when the brake pads wear out and there is only metal on metal contact?

Thanks for any help :)

2. Oct 29, 2015

### Staff: Mentor

Sparks can occur when you try to interrupt current that's flowing in a circuit that has inductance.

3. Oct 29, 2015

### CWatters

Perhaps think about the definition of torque?

4. Oct 30, 2015

### Dodsy

You have to look at your equations for torque. Where torque is equal to the torque constant times the motor current. The torque constant is based on armature length, number of wire turns, magnetic strength etc.

Kt = 2(Bnlr)
Where:
Kt is the torque constant, N is the number of loops of wire in the magnetic field, l is the magnetic field, and r is the radius of the armature.

So to increase torque you increase the torque constant or the motor current as you already said. But you can also mention wire loops, magnetic field or the radius of the armature. You're on the right track. Good luck.