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# Investigation 3 – PostLab

### ANALYZE IT

Complete the Analysis Questions in your SDR then discuss them as a class.

Analysis Questions After Trial 3:

1. Question: What effect did increasing the number of batteries have on the current flowing through the circuit?

2. Question: Did changing the number of batteries affect the strength of the electromagnet? Support your answer with data from the experiment.

3. Question: How are the current and the strength of the electromagnet related? Support your answer with data from the experiment.

4. Question: How many turns of wire were on the electromagnet?

5. Question: Measure the length of the coil in centimeters. What is the length of the coil?

6. Question: What is the length of the coil in meters? Remember 100 cm = 1 meter.

7. Calculate the value for “n” which is the ratio of the number of turns of wire (N) to the length of the coil (L) in meters. Use the following formula to calculate “n” in turns per meter.

n = N/L

8. Record: Write the values for n for each Trial in Table A.

9. Calculate the magnetic field for each electromagnet using the values for current (I), “n” and the constant μ0. Use the formula below for help. Record: Write the value for the magnetic field of each electromagnet in Table A.

B = magnetic field

μ0 = 12.57 × 10-7 Tesla-meters/amps.

n = N/L (N = number of turns of wire, L = length of the coil) I = current in amps

B = μ0nI

B= (12.57 × 10-7 Tesla-meters/amps) × (n) × I.

10. Question: Look at the formula for magnetic field. Is there a relationship between current (I) and the strength of the magnetic field (B)? Use the formula below and the explanation in the previous Background for help.

B = μ0 × n × I

11. Question: Why did changing the number of batteries affect the magnetic field of the electromagnet? Explain your answer using the formula for magnetic field again.

B = μ0 × n × I

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Analysis Questions After Trial 6:

1. Question: Calculate the value for “n” for the electromagnet with 15 turns of wire. Use the following formula to calculate turns per meter:

n = N/L

2. Question: Calculate the value for “n” for the electromagnet with 20 turns of wire. Use the following formula to calculate turns per meter:

n = N/L

3. Question: Calculate the value for “n” for the electromagnet with 25 turns of wire. Use the following formula to calculate turns per meter:

n = N/L

4. Record the values for “n” in Table B.

5. Question: Calculate the magnetic field for each electromagnet using the numbers for current, “n”, and the constant μ0.

6. Record: Write the value for the magnetic field of each electromagnet in Table B.

7. Question: How did changing the number of coils affect the number of paper clips the electromagnet could hold?

8. Question: How did changing the number of coils affect the magnetic field?

9. Question: Look at the data. Did changing the number of turns of wire change the current in the electromagnet?

10. Draw a best fit line graph to show the relationship between current and magnetic field. Use data from Table A to create the graph. Refer to the Procedures Determination and Graphing of Independent and Dependent Variables and Drawing of a Best Fit Line for assistance if necessary.

11. Draw a best fit line graph to show the relationship between the number of coils and the magnetic field. Use data from Table B to create the graph. Refer to the procedures for Determination and Graphing of Independent and Dependent Variables and Drawing of a Best Fit Line for assistance if necessary.

12. Question: Study the two graphs in problems 10 and 11. What conclusions can you make about current, the number of coils, and the strength of a magnetic field? How does this relate to the formula for a magnetic field?

### GET FOCUSED

Answer the following two Focus Questions:

What is the relationship between electricity and magnetism?

What factors affect the strength of an electromagnet?