**THE MAGNETIC
FIELD**

**ANALYSIS**

The field at the center of the Helmholtz
Pair is a combination of the field produced by the current in the coils
and the Earth’s field, which of course is always there. The field produced
by the coils is directly proportional to the current that passes through
them, , where
**k**
is the proportionality constant. We can therefore write the total field
as:

**1. **Plot
against **I**. Draw the best straight line through the points and find
the Slope **S**. Enter the value in cell **D67**. The value of k
is automatically calculated by the spreadsheet in cell **D56** from
the coil properties that you entered. Using this value, and the value obtained
for the Slope, compute

, and enter the result in cell **D69**.

The jar magnet is now calibrated
so that the magnitude of a magnetic field in which it is placed can be
determined directly from the period of oscillation by using **equation
(2)**.

**2. **From
the period measured with the jar magnet in the Earth’s field alone in cell
**D63**,
use **equation (2)** to calculate the magnitude of the horizontal component
of the Earth's magnetic field, and enter in cell **D71**. Compare the
measured value with the value listed for your location in a handbook of
physical measurements or as given by your lab instructor, and enter the
percentage error in cell
**D73**.

**3. **Submit
the completed **Worksheet** along with the graph as part of your lab
report.