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- I've conducted an experiment to work out the efficiency of a small motor, and it comes out to be very low. Have I done my calculations correctly?

Hello All

I've conducted an experiment to work out the efficiency of a small motor, and it comes out to be very low. Have I done my calculations correctly?

I connected the motor to a gearbox (made from Meccano) and a winch and used it to lift a weight. I measured the DC voltage across the motor and the current through it. Here are my results:

Motor voltage=15V, current =0.9A

The motor/gearbox/winch lifted a 0.56kgm weight 0.2m in 25 secs.

Electrical energy used = 15 x 0.9 x 25 = 337.5W secs = 337.5J

Mechanical work done = 0.56 x 9.8 x 0.2 = 1.0976Nm = about 1J

If my calculations are correct, the arrangement had an efficiency of about 0.3%, which seems very low to me. I suspect the gearbox is not very efficient, but the results are surprisingly poor (to me anyway).

Have I made a mistake in the calculations?

best regards ... Stef

Reference: https://www.physicsforums.com/forums/mechanical-engineering.101/post-thread

I've conducted an experiment to work out the efficiency of a small motor, and it comes out to be very low. Have I done my calculations correctly?

I connected the motor to a gearbox (made from Meccano) and a winch and used it to lift a weight. I measured the DC voltage across the motor and the current through it. Here are my results:

Motor voltage=15V, current =0.9A

The motor/gearbox/winch lifted a 0.56kgm weight 0.2m in 25 secs.

Electrical energy used = 15 x 0.9 x 25 = 337.5W secs = 337.5J

Mechanical work done = 0.56 x 9.8 x 0.2 = 1.0976Nm = about 1J

If my calculations are correct, the arrangement had an efficiency of about 0.3%, which seems very low to me. I suspect the gearbox is not very efficient, but the results are surprisingly poor (to me anyway).

Have I made a mistake in the calculations?

best regards ... Stef

Reference: https://www.physicsforums.com/forums/mechanical-engineering.101/post-thread