1.Objective To study magnetic fields set up by a long straight wire and solenoids using a search coil. 2.Background information -A search coil is a device for studying a varying magnetic field. When it is placed in an alternating magnetic field perpendicular to it, an alternating e.m.f. will be induced across its ends. -If a search coil is put in a magnetic field produced by passing a sinusoidal current through a long straight wire or a solenoid, the maximum induced e.m.f. across the search coil is directly proportional to the maximum magnetic field.