Hypothesis on voltage homework

[ccnv]

Homework Statement

I have make a hypothesis saying what changing voltage, magnetic field strength and number of loops in a coil in a DC motor do to effect efficiency using the efficiency equation below. I can't understand how torque is related at all.

mass and height are constant

I have no idea how to prove this

Homework Equations

efficiency equation:
Eff=(mgh/t)/VI*100

mass and height are constant

torque in a dc motor:
τ=BAIN

B is magnetic field strength
A is cross sectional area of the coil in the motor, I is current, N is the number of loops in the coil.How can i find torque by timing how long it takes a motor to lift a constant mass at a constant height? Maybe that doesn't make sense? I don't even know anymore...

 

[Redbelly98]

Homework Statement

I have make a hypothesis saying what changing voltage, magnetic field strength and number of loops in a coil in a DC motor do to effect efficiency using the efficiency equation below. I can't understand how torque is related at all.

mass and height are constant

I have no idea how to prove this

Homework Equations

efficiency equation:
Eff=(mgh/t)/VI*100

mass and height are constant

torque in a dc motor:
τ=BAIN

B is magnetic field strength
A is cross sectional area of the coil in the motor, I is current, N is the number of loops in the coil.


How can i find torque by timing how long it takes a motor to lift a constant mass at a constant height? Maybe that doesn't make sense? I don't even know anymore...

You can get the force applied to the mass being lifted. You also need to know the distance from the string or rope (that lifts the mass) to the rotation axis of the motor. Often this is simply the radius of a wheel that the string is wound around.

From force and distance, you can calculate what the torque is.