This key experiment enables the calculation of power of a small electric motor as it raises a mass.

Curriculum Topics
o Electrical circuits
o Energy and power

Description
In this experiment, you will study a small, inexpensive electric motor used as a crude elevator. You will measure the current through and voltage (potential difference) across, a motor as it lifts a small mass. If you know the current and voltage, you can calculate another electrical quantity—power.

Principle
The unit of power is the watt (W). An electrical device that consumes 1 W converts one joule of energy to another form every second (1 J/s). If the power provided to a device is constant over time, you can multiply the power by the time and get the energy. If the power provided to a device changes during the experiment, the electrical energy can be determined by finding the average power x time or finding the area (integral) under a power vs. time graph.

Tasks
• Determine the electrical energy used by the motor and compare it to the change in gravitational potential energy of the mass.
• Calculate the efficiency of the motor as a machine used for lifting.

Ideas for Extended Investigations
• Investigate the efficiency of the motor at different speeds using the same load.
• Try other motors and see if you can find more efficient ones.
• Use a Temperature Probe to monitor the temperature change of the motor.
• Use your motor as a generator. Take current and voltage data of the power generated by the falling mass as it turns the motor. Compare the power measured by the interface to the change in gravitational potential energy of the falling mass.

Last edited 22nd Aug 2018