Interactions between Interactions between Electricity and Electricity and MagnetismMagnetism

Interactions between electricity and Interactions between electricity and magnetism all involve some motion of magnetism all involve some motion of either charges (electricity) or changes in either charges (electricity) or changes in the magnetic field.the magnetic field.

Mag/Elec InteractionsMag/Elec Interactions

Magnetic ForceMagnetic Force There is a magnetic force whenever a There is a magnetic force whenever a

charge (or charged object) moves across a charge (or charged object) moves across a magnetic field.magnetic field.

The Force direction obeys the Right hand The Force direction obeys the Right hand rule we discussed in class.rule we discussed in class.

The equation for this is F = q v BThe equation for this is F = q v B q = amount of charge (C), v = velocity, B = q = amount of charge (C), v = velocity, B =

magnetic field (Teslas)magnetic field (Teslas)

Magnetic Force on Magnetic Force on moving chargemoving charge

Mag/Elec InteractionsMag/Elec Interactions

Right Hand Rule # 1Right Hand Rule # 1 Point fingers in direction of moving charge qPoint fingers in direction of moving charge q Orient your palm so it’s facing the direction Orient your palm so it’s facing the direction

of the magnetic field Bof the magnetic field B Extend your thumb, it’s the direction of the Extend your thumb, it’s the direction of the

force.force. This force happens only when the charge This force happens only when the charge

moves perpendicular to the magnetic field B.moves perpendicular to the magnetic field B.

Right hand rule for Right hand rule for magnetic forcemagnetic force

Mag/Elec InteractionsMag/Elec Interactions

A wire carrying a current creates it’s own A wire carrying a current creates it’s own magnetic field.magnetic field.

This field is circular and its orientation is This field is circular and its orientation is determined by Right hand rule #2determined by Right hand rule #2

Mag/Elec InteractionsMag/Elec Interactions

Right Hand Rule # 2: to determine the Right Hand Rule # 2: to determine the direction of the circular magnetic field direction of the circular magnetic field around a wire carrying a current.around a wire carrying a current.

Direct your thumb along the wire in the Direct your thumb along the wire in the direction of the current.direction of the current.

Your fingers curl in the direction of the Your fingers curl in the direction of the circular magnetic fieldcircular magnetic field

Mag/Elec InteractionsMag/Elec Interactions

Electro-magnetsElectro-magnets If you coil a wire into a helical form (like wrapping a If you coil a wire into a helical form (like wrapping a

wire around a cylinder) and run a current through it, wire around a cylinder) and run a current through it, each circular coil creates a small mag field. each circular coil creates a small mag field.

The mag field from each coil “adds up” to create The mag field from each coil “adds up” to create what looks like a magnet with a North and South what looks like a magnet with a North and South pole.pole.

By running a current through this wire, you “make” a By running a current through this wire, you “make” a magnet. This is also known as a solenoid.magnet. This is also known as a solenoid.