Lab Analysis #2 - Magnetic Field from a Curent-Carrying Wire

Lab Analysis Guidelines

The purpose of this assignment is to work on analyzing data, drawing meaningful conclusions from the data, and supporting the conclusions with evidence and physical reasoning. Analysis:

• Present your data/results (usually a graph or multiple graphs). • Include units on all numeric values included in the analysis. • Report the measured and theoretical values for any constant measured from the data (e.g.

the acceleration due to gravity), as well as the percent difference. • State the source of the theoretical value.

Graphs

• On graphs, include axis labels, units, a title and description (e.g. Figure 1. Graph showing… See how figures are presented in our book for examples.), best fit curve, equation displayed, and an appropriate scale.

Explanation:

• Explain what the data/results tell you. • State what model best describes the data. • Describe features of the graph that support your conclusion about the model. • Use physical reasoning about how the system behaves in limiting cases to support your

conclusion about the model.

Equations:

• Write out the model as an equation with symbols that represent physical quantities. (See how equations are presented in our book for examples.)

• Include the equation on its own line. • Define any symbols used in the equations.

Uncertainty and Mistakes:

• Identify the largest source of uncertainty in the data collection. These are limitations of the measurement tools and experimental procedure.

• Identify any mistakes made in doing the experiment, if there are any.

Format:

• Write in paragraph form with complete sentences for all descriptive sections. • Write clearly and concisely and for a technical audience. • Write in a first-person, active voice. (e.g., "We conclude that..." rather than "It was

concluded that...") • Use correct spelling, grammar, punctuation, tone, etc..

Sample Lab Analysis Results and Analysis: Plotting a graph of circumference vs. radius for the circles (Fig. 1) produces a linear graph with a y-intercept of approximately zero. This implies a proportional relationship between the circumference of a circle and its radius. The relationship can be written as:

C = kr, where C is the circumference, r is the radius, and k is the constant of proportionality. Physically

the proportional relationship makes sense because if the circle had a radius of zero, there would be no circle, and thus no circumference. We determined the constant of proportionality by fitting the data with a linear function, yielding a slope of 6.26. Our measured constant of proportionality differs by 1.9% from the well established value of 2π. The difference between our measured value and the established value results from the accuracy of laying string around the outside of the circle to measure its circumference.

Figure 1: Graph showing the relationship between the circumference of a circle and its radius.

ci rc

um fe

re nc

e (c

m )

radius (cm)