Introduction

When an electric current flows through a wire, a magnetic field is produced around the wire. The magnitude and direction of the field depends on the shape of the wire and the direction and magnitude of the current through the wire. If the wire is wrapped into a loop, the field near the center of the loop is perpendicular to the plane of the loop. When the wire is looped a number of times to form a coil, the magnetic field at the center increases. A solenoid is formed when many turns of wire are wrapped around a tube. Solenoids and coils are used in electronic circuits or as electromagnets. 

In this lab, you will examine how the magnetic field is related to both the number of turns in a coil and the current through the coil with a magnetic field sensor. A complication that must be considered is that the sensor will also detect the earth's field and any local fields due to electric currents or some metals in the vicinity of the sensor.

A Slinky will be used to study a solenoid. By inserting a magnetic field sensor between the coils of the Slinky you can study how the field varies in different parts of the solenoid. You will also measure the permeability constant a fundamental constant of physics.