Efficiency of a Motor

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Jessica Roper 11H

Efficiency of a Motor

Aim: To investigate the relationship between the efficiency of a motor and the load it is lifting.

Apparatus:

Safety

You should not use an electrical source with wet hands. Sockets should have nothing inserted into them other than plugs. This is because the voltage of a mains supply is 240V and this is enough to kill a human being. Water should be kept away from sockets, as water is a good conductor of electricity and therefore could potentially be lethal. For the same reason all wires should be insulated. As a general safety rule there should be no running in the laboratory and all bags should be placed under desks to avoid tripping.

Diagrams

Preliminary Results

From my preliminary experiments I discovered that the cotton would not fix itself to the spindle of the motor in such a way that it would wind up without the addition of blue tack to secure it. It is vital therefore that I use blue tack in this experiment or the efficiency of the motor cannot be calculated because the load would not move any distance whatsoever. I attempted to gain results for 0.01 Kg but this proved to be too difficult as the time taken for the motor to lift the mass was too quick to measure with any degree of accuracy. In addition, the load tended to swing whilst being lifted and this would have affected the results in an unfair way. The largest load I will use will be 0.1 Kg as beyond this I discovered that the cotton found it difficult to support the load and this would have affected my results. I will use the following loads because they will produce results which are close enough together to draw an accurate graph: 0.02 Kg, 0.04 Kg, 0.06 Kg, 0.08 kg and 0.1 Kg. I plan on using a distance of 0.5 M as this gives a large enough distance for measuring the time it takes for the load to be lifted. Equally it is a suitable length to easily wind around the spindle of the motor and be used in conjunction with the clamp. The voltage I shall use will be 2V as this allows the motor to work at a good, suitable speed for us to measure the time it takes for the load to be lifted. Using this voltage results in the amperage remaining at 1.36 A

This shows that the efficiency increases and then decreases again. This gives me an indication of what the results for my experiment shall be like and will help me to write my hypothesis.

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Fair Testing

  • The voltage must be kept the same. This is because the motor will turn at a different speed depending on the voltage and the rate of the motor affects the time it takes for a load to be lifted.
  • The length of cotton must be kept the same as the distance affects the kinetic energy. The shorter the cotton is the faster the load will lifted, such a change will therefore produce results that are not relevant to each other. Also the cotton itself must be kept the same as different thicknesses of cotton could wind ...

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