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venom201

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## Homework Statement

A student is asked to supply an electric motor with 1.0 mA of current at 3.0 V potential difference.

a. Determine the power to be supplied to the motor.

b. Determine the elctrical energy to be supplied to the motor in 60s.

c. Operating as designed, the motor can lift a .012 kg mass a distance of 1.0 m in 60s at a constant velocity.

d.To operate the motor, the student has available only a 9.0 v battery to use as the power source and 5 resistors: 1000 [tex]\Omega[/tex], 4000 [tex]\Omega[/tex], 4000[tex]\Omega[/tex], 5000[tex]\Omega[/tex], 10000[tex]\Omega[/tex].

How should the circuit be wired to power the motor.

## Homework Equations

P= IV

efficiency = output/input

## The Attempt at a Solution

a. (.001)(3)= .003 watts

b. Not too sure about this, I just multiplied the .003 by 60 to get .18 watts

c. mgh= (.012)(10)(1)= .12

So do I divide .12 by the answer from part b?, I feel like I'm missing a step in there.

d. For this I'm completely lost, I know the motor should be in parallel with another branch of the circuit but I'm not sure which resistors to use.