Physics - Motor Efficiency

Physics Coursework - Motor Efficiency

In everyday life motors are used all around us, all of the time, in dishwashers, toy cars, or washing machines. So I thought it would be interesting to see how a motor reacts under varying conditions.

In this experiment a weight is suspended by a thread attached to the axle of a small motor. As the motor turns, the thread is wound around the axle to lift the weight. I will be investigating how the efficiency changes when the mass of the weight increases.

Variables:-

Voltage- The voltage applied to the motor.

Weight- The weight lifted by the motor.

Time- The time the motor is switched on.

The variable I have chosen to vary is the mass of the weight, I have chosen “weight” as a variable because it is not difficult to vary and I predict that it will give me reliable results into my investigation about the efficiency of a motor.

I chose to keep the voltage constant to make the experiment fair

Apparatus setup diagram below:-

Method:-

Set the weights to the mass you want to measure and set the voltage to read 6 volts.

Connect the motor to the power supply keeping the voltage at a constant 6.

Then measure the time, current, mass, and the voltage (constant).

Prediction:-

This is a preview of the whole essay

Apparatus setup diagram below:-

Method:-

Set the weights to the mass you want to measure and set the voltage to read 6 volts.

Connect the motor to the power supply keeping the voltage at a constant 6.

Then measure the time, current, mass, and the voltage (constant).

Prediction:-

I predict that when the mass increases, the efficiency will increase to a maximum and then decrease. This is because with no weight the motor will consume energy just to turn and do no useful lifting, giving 0% efficiency. When the weights are too heavy the weights will not lift at all, the motor will then heat up, and there will be 0% efficiency too. In between the efficiency will vary depending on the mass of the weight. If the mass is high the efficiency will also be high, if the mass is low, the efficiency will be low too. I predict there will be a point where the efficiency starts to decrease.

Obtaining Evidence:-

Results table 1:-

Results table 2:-

I recorded two sets of results to increase the reliability of the information, I then created an average graph of the results.

Average results table:-

Analysing and considering evidence:-

The evidence collected shows that my results agree with my prediction. The graph shows that there is a point at which the efficiency starts to decrease, but like I predicted, the efficiency increases with the weight until a point (between 0.20-0.30kg). The point at which the efficiency started to decrease was just under 25%.

Until this point, the efficiency increases with the increase of load but then after this point the efficiency of the motor starts to decrease as the load increases still.

The reason for the efficiency of the motor decreasing is because after a certain point, or load, the weight is too heavy for the motor to act efficiently. If the load is too great the motor will be under much strain and the efficiency will decrease. To stop this from happening the voltage applied to the motor could be increased.

Evaluation:-

This experiment was conducted using a computer generated program so the results which were obtained were expected to be accurate. Looking at the evidence I have collected, including the graph I can see the results obtained were the results I predicted would occur.

From my graph there were no anomalous results which I obtained, this shows my results were accurate. The method was suitable for the experiment conducted. It was a relatively simple experiment and did not involve any complicated apparatus or measurements. I would not change anything to do with the method because the results I obtained were accurate. The setup is very simple but effective for the type of experiment it was.

My results were reliable and were the results which I predicted, from my results I can form a firm conclusion.

Conclusion-

As the load increases so does the efficiency of a motor, until a certain point, at this point the efficiency starts to decrease because the load is too great.

To further this experiment I would investigate how voltage and time effect the efficiency of a motor.