Independent Variable
Independent variables are variables that are not affected by any other variables. They can be made to direct a change in the dependent variables. Students, for this lab, are required to state and list the independent variables that are being dealt with. The independent variable should be stated after considering the possibilities and analyzing all aspects of the experiments. Usually there is only one independent variable unless a research paper is being submitted in which case more are possible.
Dependent Variable
Dependent variables are influenced by the independent variable stated previously. Once again, students are required to list all the dependent variables that were encountered during the experiments, as how the independent variables affected these dependent variables have to be investigated.
Controlled Variable
It is important to note that a controlled variable is not influenced by any other variables and will not affect any other variable either. These variables are kept constant to make sure the other variables are analyzed and tested fairly. Students are once again required to list all the controlled variables that were encountered throughout the experiment.
Hypothesis
“From the formula that will be used to investigate the effects that the factors have towards the strength of the electromagnet, I believe that that when the number of turns the insulated wire makes on the nail, and the value of the current running through the wire increases, then obviously the value of the magnetic field will also increase. Due to the fact that they are both directly proportional strengthen this case. Since the Magnetic field around the nail increases, its ability to attract more paperclips will also increase and so when these two factors do increase then the number of paperclips attracted to the nail will also increase”.
Since the instructor has provided a hypothesis, it is the students turn to formulate a reasonable hypothesis while backing it up with theoretical values as well as concepts.
Materials
- Several 1.5 V Batteries (Fresh)
- Ammeter to check the current
- Battery Holders
- Insulated wire to be coiled around the nail
- Iron Nail with a constant length
- Paper Clips
- Paper and a writing utensil to record the data
- Alligator clips to connect the circuit
Procedure
When keeping the # of turns constant:
- Take the nail and coil it around with insulated wire and make sure that the distance between the turns is constant and keep circulating for 7 turns.
- Pick out one battery, an Ammeter, and the nail with the coiled wire.
- Connect them in a series circuit and check the current. Attempt to add as many paperclips as possible to the iron nail with the insulated wire which is now acting as an electromagnet.
- Record the results and add another battery to the series, and check the current. Once again attempt to place as many paperclips as you can on the Electromagnet, and record the results.
- Redo steps 3 and 4 by adding more batteries one by one each time, checking the current, and checking how many paperclips the Electromagnet can hold. The maximum and final amount of batteries that should be used is 7.
- Now that all the data has been obtained, process the data by drawing a data chart and graph the points. On the graph, draw the line of best fit, and give the graph the title: “Graph to show Current vs. Paperclips graph.”
When keeping the current constant:
- Pick up one 1.5 volt battery and form a series circuit connecting the alligator clips from the battery to the wire on the nail.
- Start with 7 turns on the nail, as this will be the initial amount of turns on the nail. Remember that the wire cannot touch another part of the wire when coiled.
- Take an Ammeter and add it to the series circuit with alligator clips and check the current.
- Record the constant current and you will be ready to begin the main experiment.
- At this point, disconnect the series circuit by disconnecting the Ammeter from the circuit and just leave it with the battery and the nail.
- Once connected, add as many paperclips as you can to the Electromagnet.
- Record how many paperclips these 7 turns can hold, and after that disconnect the series and change the turns to 8 turns, Redo the series circuit and connect as many paperclips again.
- Record the results for these 8 turns. From now on, keep adding turns to the Electromagnet and checking how many paperclips it can hold. Keep doing this until you have results for about 13 turns.
- Since you have finished the lab at this point, it is the time to process the data by drawing a Data chart and graphing the points. On the graph, draw the line of best fit, and give the graph the title: “Graph to show Turns vs. Paperclips.”
Figure 1: A schematic diagram depicting a simple series circuit with a battery and a nail as an electromagnet. The ammeter can be inserted to find the current passing through.
Data Processing
Data Chart for # of turns keeping constant:
Data chart for constant current:
Data Graphs
Draw a graph that shows the relationship: “Current vs. Paperclip” as well as a graph showing the relationship: “Turns-Paperclip,” using the data obtained. Both these graphs should show the line of best fit, and the uncertainties at each point.
Uncertainty:
State all uncertainties that you encountered while executing this experiment. Also, state the procedural uncertainty as well as the instrumental uncertainty (if there are any present in this lab). Create a procedural and instrumental uncertainty chart if necessary.
Random Errors:
Random errors are statistical fluctuations in the measured data due to the precision limitations of measurement devices. These types of errors usually result from the experimenter’s inability to take the precise measurements in exactly the same way all the time. Unlike, systematic errors, random errors can be evaluated through statistical analysis and can also be reduced significantly by taking the average of a large number of trials/observations. The students are required to list all significant random errors that were encountered.
Systematic Errors:
Systematic errors are reproducible inaccuracies that are consistently in the same direction, and are most of the time due to a problem which persists throughout the entire experiment. Systematic errors are hard to detect and cannot be statistically analyzed. This is because all of the data is not accurate on the same direction (either too low or too high). These errors produce a result that differs from the true value by a fixed amount, and are direct results of inaccuracy added by human and instrumental factors. It is important to find and correct systematic errors. The students are required to list all the significant systematic errors that were encountered during the lab process.
Discussion Questions
- Was there any other factors that could be tested for, and if there are what is it and how can it be tested?
- What can we conclude from the slopes of both graphs? Explain your reasoning.
- What does happen when more turns were coiled onto the nail? Does the amount of paperclips increase or decrease as you add more turns? Explain why it increases or decreases?
- What does happen when more current was running around the series circuit? Does the amount of paperclips increase or decrease as you add more current into system? Explain why it increases or decreases?
- What types of uncertainties were present in your experiment and how could they be reduced or prevented next time?
Conclusion and Evaluation
Upon completion of the lab, students should have acquired a more than rough idea of how electromagnets work and what factors can be increased/decreased to enhance/increase the intensity of the magnetic field. Students are now asked to write a formal conclusion with proper justification based on interpretation of the data that they have gathered. It is important that students figure out if their hypothesis was correct or not and if not, explain why. As in all labs, it is important to evaluate the weaknesses and limitations of the labs as well as suggesting realistic improvements to increase accuracy and eliminate as many errors as possible.
