Motor Efficiency Practical - Physics

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Stage 1 Physics – Practical
Aim: To calculate the weight limit held and the efficiency of an electric motor. Method:
1.) With all materials gathered, start by plugging the Power Supply Unit (PSU) into a free plug, making sure the PSU is switched to 6V. 2.) Attach the Crocodile clips from the PSU to the ammeter and motor as shown above in the labelled diagram, making sure the voltmeters clips are attached to the motor. 3.) Starting with 20g of weight attached to the string on the motor (as seen above) perform 3 experiments with each weight group (20g, 40g, 60g, 80g) and record their voltage, time and current. 4.) Have one person reading the ammeter, one person timing the weights reaching the top of the motor, and the other person both switching on the motor and reading the voltmeter. 5.) Perform these 12 experiments and record all data in your book with format similar to the results below. 6.) Pack up your materials and return them to their original places. Safety Instructions:

1.) Keep all electrical equipment away from the taps / access to water 2.) Keep the Voltage set to 6 at all times
3.) Keep fingers away from motor, make sure motor and PSU are switched off after experiments 4.) Don’t play around with the materials and apparatus’s! Results Table:
Mass (g)| Time (t)| Current (A)| Potential Difference (V)| 20| 0.70| 0.72| 5.06|
20| 0.60| 0.72| 5.06|
20| 0.66| 0.71| 5.04|
40| 0.70| 0.95| 5.00|
40| 0.84| 0.84| 5.00|
40| 0.72| 0.88| 5.00|
60| 1.2| 0.99| 5.02|
60| 1.18| 1.05| 5.02|
60| 1.14| 1.2| 5.02|
80| 2.9| 1.12| 5.08|
80| 3.9| 1.08| 5.08|
80| 3.15| 1.19| 5.07|
Average 20| 0.65| 0.72| 5.05|
Average 40| 0.75| 0.89| 5.00|
Average 60| 1.17| 1.08| 5.02|
Average 80| 3.32| 1.13| 5.08|

Calculations:
Calculating the Input Energy –> E = V x I x T (Electric Energy = Voltage x Current x Time) (averages) Calculating the output Energy –> = m x g x h (Gravitational P.E = mass x gravity x height) (averages) 20g Input energy = V x I x T = 2.363420g Output Energy = m x g x h = 0.177184 40g Input Energy = V x I x T = 3.337540g Output Energy = m x g x h = 0.354368 60g Input Energy = V x I x T = 6.343360g Output Energy = m x g x h = 0.531552 80g Input Energy = V x I x T = 19.06 80g Output Energy = m x g x h = 0.708736 (Gravity = 9.8, height = 90.4cm or 0.904m)

20g Efficiency = (Output/Input) x 100% = (0.177184/2.3634) x 100% = 7.49% 40g Efficiency = (Output/Input) x 100% = (0.354368/3.3375) x 100% = 10.62% 60g Efficiency = (Output/Input) x 100% = (0.531552/6.3433) x 100% = 8.38% 80g Efficiency = (Output/Input) x 100% = (0.708736/19.06) x 100% = 3.72%

Graphed Results:

Sources of Error: (How does procedure limit errors??)
The procedure that is given in step by step order limits errors by the use of extra safety measures. The additional safety procedures limit the chance of electrical equipment being damaged, danger being caused, therefore harming the students, and the experiment failing. The simple steps seen in the method are easy to follow and can be instructed by a teacher to a class. The materials are given in the circuit diagram and are relisted in the steps above. The diagram shown above also supports the steps if the student is confused to how the circuit should be setup and the method further describes the required people in a group and who does what. Common sources of error that will be found in this experiment if done incorrectly are the setup of materials, reaction of the timer and organisation and cooperation of the group members. If not connected correctly, the motor may burn therefore causing either injury or the power to short circuit, becoming a hazard to other class members. During the process, after each experiment, the switch on the motor and the power supply must be turned off. To minimise sources of error, the group members should be constantly...
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