1. Starter What effect does an iron core have on the magnetic field of a coil? ( What role does the nail play?) What effect does an iron core have on the magnetic field of a coil? ( What role does the nail play?)

2. Magnetic Field of a Coil The magnetic field inside a coil that has N turns, is L long, and has a current of I, is given by: B =  o iN/L i = current in amps N = # of turns L = length in meters  o = 1.25 x 10 -6 The magnetic field inside a coil that has N turns, is L long, and has a current of I, is given by: B =  o iN/L i = current in amps N = # of turns L = length in meters  o = 1.25 x 10 -6

3. Example Find the magnetic field inside a coil that is 8cm long, has 3000 turns, and carries a current of 1.00 amp. Find the magnetic field inside a coil that is 8cm long, has 3000 turns, and carries a current of 1.00 amp. B =  o iN/L = (1.25 x 10 -6 )(1.00)(3000)/.08 =.0469T Note: Gauss is another common unit for B-fields ( 10,000 Gauss = 1Tesla) so B =.0469T( 10,000Gauss/1 Tesla) = 469 Gauss

4. Iron Core Solenoids The magnetic field inside a coil that has N turns, is L long, has a current of I, and has an iron core is given by: B = k  o iN/L i = current in amps N = # of turns L = length in meters  o = 1.25 x 10 -6 k ≈ 200 for iron The magnetic field inside a coil that has N turns, is L long, has a current of I, and has an iron core is given by: B = k  o iN/L i = current in amps N = # of turns L = length in meters  o = 1.25 x 10 -6 k ≈ 200 for iron

5. Example Find the magnetic field inside a coil that is 8cm long, has 3000 turns, and carries a current of 1.00 amp, and has an iron core. Find the magnetic field inside a coil that is 8cm long, has 3000 turns, and carries a current of 1.00 amp, and has an iron core. B = k  o iN/L = 200(1.25 x 10 -6 )(1.00)(3000)/.08 = 9.38T

6. Starter Which direction is the magnetic field in the center of the coil? Right or Left?

7. Starter Which battery terminal is positive, and which is negative?

8. Magnetic Field of a Coil The magnetic field inside a coil that has N turns, is L long, and has a current of I, is given by: B =  o iN/L i = current in amps N = # of turns L = length in meters  o = 1.25 x 10 -6 The magnetic field inside a coil that has N turns, is L long, and has a current of I, is given by: B =  o iN/L i = current in amps N = # of turns L = length in meters  o = 1.25 x 10 -6

9. Part 1: Magnetic Field of a Coil

10. Data Part 1 Logger-pro Using the Vernier magnetic field detector, a coil, the power supply on the circuit board, and a current sensor, determine the magnetic field inside two different coils for a given current. Use this value to determine the number of turns in each coil. N = (BL/  o i) Coil DescriptionLength, L(m)Current I(A)Magnetic Field, B(T)N ( calculated)

11. Part 2 The Earth’s Magnetic Field Vernier – Loggerpro Using the Vernier magnetic field detector: 1. Determine the magnetic field of the Earth by rotating the magnetic field sensor until you obtain the largest reading possible. 2. Determine the Inclination of the field in degrees. This is the angle between the horizontal and the sensor. 3. Check your data with NOAA website. http://www.ngdc.noaa.gov/geomag-web/ Vernier – Loggerpro Using the Vernier magnetic field detector: 1. Determine the magnetic field of the Earth by rotating the magnetic field sensor until you obtain the largest reading possible. 2. Determine the Inclination of the field in degrees. This is the angle between the horizontal and the sensor. 3. Check your data with NOAA website. http://www.ngdc.noaa.gov/geomag-web/

12. Part 3 The Field of a Bar Magnet Vernier – Loggerpro 1. Using the Vernier magnetic field detector: Determine how the magnetic field of a bar magnet depends on the distance from the end of the magnet. 2. Plot B vs. x. and fit with a smooth curve. Vernier – Loggerpro 1. Using the Vernier magnetic field detector: Determine how the magnetic field of a bar magnet depends on the distance from the end of the magnet. 2. Plot B vs. x. and fit with a smooth curve. Distance From Magnet (cm) Magnetic Field (T) 2 4 6 8 10 12 14 16 18 20

13. Connection Where do you encounter magnetic coils every day?

14. Questions 1.How did you values of the Earth’s Magnetic Field and Inclination compare to the NOAA values? 2.Is the relation between the B -field of a bar magnet and the distance from the end linear? Explain.

15. Exit Write down the formula for the B-field in a coil and describe each term. Write down the formula for the B-field in a coil and describe each term.

16. Report Checklist A.Part I Data table with Calculations Shown B.Part II Experimental value of B for Earth and Inclination Angle C.Part II NOAA Value for B and Inclination Angle D.Part III Data table and Graph E.Questions F.Starter G.Connection H.Summary