Electromagnets Currents in wires create a magnetic field around the wire By turning the current on and off, you can control the magnetic field You can control the magnetic field
Solenoids Magnetic field around current carrying wire forms a cylinder around the wire If wire is twisted into a loop, magnetic field lines are bunched up in the loop Strength in magnetic field lines increase as number of loops increase By winding the wire into a coil, you have strengthened the field into the center of the coil The two ends of the coil act as poles A current carrying coil of wire with many loops is called a solenoid A solenoid is a magnetic field that can be turned on and off by switching the current off or on
Multiplying Magnetism When a ferromagnetic material such as iron is placed in a solenoid, the magnetic field is increased When a ferromagnetic material is placed in a solenoids magnetic field, it acts as a magnet A solenoid with a ferromagnetic core is an electromagnet An electromagnet is a strong magnet that can be turned on and off Electromagnets can be used for lifting scrap metal
Increasing the Strength of an Electromagnet Use a stronger ferromagnetic core, add more and closer coils to the solenoid, add more loops in the wire, or increase the current.
Recording Information When you record information on computer disks or credit cards, you are using electromagnets When you talk into a microphone, the current changes with the vibration of your voice Since the current changes, so does the magnetic field