PHY 132 - Magnetic Field worksheet

1 M A G N E T I C F I E L D S – W O R K S H E E T Name: Andrew Crist Partners: Hunter, Nahom, Zainab TA: Rekha Joshi DATA & ANALYSIS Part 1 – Earth’s Magnetic Field Deflection Angle (deg) Current (units: mA) 20 2.81 30 5.41 40 7.55 50 9.66 60 14.43 • Slope of the tan (࠵?) vs ࠵? graph: .1187 (units: mA/theta) • ࠵? ! calculated from the slope: .025 (units: tesla) • Does your calculated ࠵? ! fall within the expected range? (0.25 – 0.65 Gauss): no Calculations .1187 = ((4pi*10^-7)(500))/(2(.107)Be) Be = .0247 Part 2 - Magnetic Force on a current-carrying wire Scale Reading (in grams) Scale Reading (in kg) ࠵? ࠵? = Scale Reading (kg) x 9.8m/s 2 (in N) Current I (in A) .11 .0011 1.12 *10^-4 .151 .15 .0015 1.53 *10^-4 .303 .17 .0017 1.73 *10^-4 .455 Clean-up (3): Data (20) & Plots (25): Analysis (30): Post-Lab (10): Total (88):

2 .24 .0024 2.45 *10^-4 .609 .33 .0033 3.37 *10^-4 .755 .35 .0035 3.57 *10^-4 .908 • Slope of the ࠵? ࠵? vs ࠵? graph: .00401 (units: N/A) • Length if the bottom side of the wire: 6.5 (units: cm) • ࠵? calculated from the slope: .062 (units: tesla) • ࠵? from direct measurement: .0617 (units: tesla) • % difference: .49% Calculations B = slope/L = .00401/.065 = .062 %difference = (calculated-measured)/avg = .49% POST-LAB QUESTIONS 1. In Part 1 you actually calculated the strength of the ambient magnetic field, which could come from a variety of different sources. In addition to the Earth’s magnetic field, list some other sources of the ambient magnetic field in the lab. Which source do you think provides the largest contribution to the overall magnetic field? The largest contribution besides the lab equipment would definitely be that of the earth’s magnetic field. It is the great strength of this field that allows magnets to function. Other sources include nearby computers, wiring throughout the walls, nearby power lines, etc. 2. At what angle of deflection makes the magnetic field strength produced by the coil of wire equal to the ambient magnetic field? A small drawing might be helpful. Hint: see Figure 1. Tan(theta) = Bc/Be If theta equals 45 degrees then tan(theta) equals 1. This would make the ratio between Bc and Be 1 as well, meaning the two values are equal.

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