Magnets have two ends – poles – called north and south. Like poles repel; unlike poles attract. If you cut a magnet in half, you don’t get a north pole and a south pole – you get two smaller magnets. Only iron, cobalt, nickel, gadolinium, and some of their oxides and alloys show strong magnetic effects. Magnetic poles are different from electric charges due to the fact that electric charges can be separated and isolated, however magnetic north or south poles can not be separated and isolated.

Magnetic fields can be visualized using magnetic field lines, which are always closed loops. The Earth’s magnetic field is similar to that of a bar magnet. Note that the Earth’s “North Pole” is really a south magnetic pole, as the north ends of magnets are attracted to it. Surrounding a magnet, there is a magnetic field. Like an electric field, a magnetic field has both magnitude and direction. The magnetic field at any point is tangent to the magnetic field line at that point. The strength of the magnetic field is proportional to the number of lines per unit area.

A uniform magnetic field is constant in magnitude and direction. The field between these two wide poles is nearly uniform. The magnetic field between two wide poles of a magnet is nearly uniform, except at the edges.

A charged particle, placed in a magnetic field, will experience a magnetic force if…. -The charge is moving - The velocity of the moving charge has a component that is perpendicular to the magnetic field. This picture shows a charge moving parallel to the magnetic field (B), which results in no magnetic force on the charge. This picture shows a charge moving perpendicular to the magnetic field (B), which results in a maximum magnetic force on the charge. The magnetic force (F) is perpendicular to both the velocity (v) and the magnetic field (B).

Right Hand Rule for Force Fingers point in direction of magnetic field B. Thumb points in direction of the velocity vector v. Palm shows the direction of the force F. Magnetic Force Charge Magnitude Velocity of charge Magnitude of magnetic field Angle formed between magnetic field direction and velocity vector.

The magnitude B of the magnetic field at any given point in space is defined as: SI Unit of Magnetic Field: newton. second coulomb. meter = 1 Tesla (T) 1 Tesla (T) is also written as 1 T = 1 N/(A. m) Nicola Tesla ( )

As a charge moves through an electric field, its path is curved in the direction of the electric field lines. This is due to the electric force acting parallel to the electric field and perpendicular to the velocity vector. As a charge moves through a magnetic field, its path is curved upward along a vertical plane. This is due to the magnetic force acting perpendicular to both the magnetic field and the velocity vector.

The magnetic force always remains perpendicular to the velocity and is directed toward the center of the circular path. The magnetic force acts as the centripetal force on the charge. The stronger the magnetic field, the shorter the radius and therefore, a “tighter” circular path. The magnetic force does no work on the charge, therefore the kinetic energy of the charge does not change.

A magnet exerts a force on a current-carrying wire. The direction of the force is given by a right-hand rule. The force on the wire depends on the current, the length of the wire, the magnetic field, and its orientation. Magnetic Force CurrentLength of Wire Magnitude of magnetic field Angle formed between magnetic field direction and wire orientation.

Using the right-hand rule, a leftward directed force results. Using the right-hand rule, a rightward directed force results.

Experiment shows that an electric current produces a magnetic field. The direction of the field is given by a right-hand rule. Right Hand Rule for Current: Grasp the wire with your right hand so that your thumb points in the direction of the conventional current; then your fingers will encircle the wire in the direction of the magnetic field.

The right hand rule indicates the direction of the magnetic field in a looped wire.

The field is inversely proportional to the distance from the wire: The constant μ 0 is called the permeability of free space, and has the value:

If currents are in the same direction, wires attract. If in opposite direction, wires repel. The magnetic field that one current creates can exert a force on another nearby current. This is the opposite of the rule for charges: like charges repel, opposite charges attract. Using the two right hand rules, one for finding the direction of the B-field of a wire, and the other for the direction of force on a wire, one can predict the results above.

The magnetic field produced at the position of wire 2 due to the current in wire 1 is: The force this field exerts on a length l 2 of wire 2 is: