Magnetic Fields – Magnetic Fields – Long Straight WireLong Straight Wire

A current-carrying A current-carrying wire produces a wire produces a magnetic fieldmagnetic field

The compass needle The compass needle deflects in directions deflects in directions tangent to the circletangent to the circle The compass needle The compass needle

points in the direction points in the direction of the magnetic field of the magnetic field produced by the produced by the currentcurrent

Direction of the Field of a Direction of the Field of a Long Straight WireLong Straight Wire

Right Hand Rule Right Hand Rule #2#2 Grasp the wire in Grasp the wire in

your right handyour right hand Point your thumb in Point your thumb in

the direction of the the direction of the currentcurrent

Your fingers will Your fingers will curl in the direction curl in the direction of the fieldof the field

Magnetic Field of a Magnetic Field of a Current Loop – Total FieldCurrent Loop – Total Field

Magnetic Field of a Magnetic Field of a SolenoidSolenoid If a long straight If a long straight

wire is bent into a wire is bent into a coil of several coil of several closely spaced closely spaced loops, the resulting loops, the resulting device is called a device is called a solenoidsolenoid

It is also known as It is also known as an electromagnet an electromagnet since it acts like a since it acts like a magnet only when it magnet only when it carries a currentcarries a current

Length L

Magnetic Field in a Magnetic Field in a Solenoid, finalSolenoid, final

The field lines of the solenoid resemble The field lines of the solenoid resemble those of a bar magnetthose of a bar magnet