Ch 22 Magnetism

CH 22 Magnetism Subject

Relevant Equations

Magneti c Field

Magneti c Force on Moving Charges

Magneti c Force RightHand Rule (RHR

Magnitude of the Magnetic Force, F F=qvBsinΘ S.I.=N Definition of the Magnitude of the Magnetic Field, B B=F/qvsinΘ S.I.= 1 tesla = 1 T = 1 N/A (A•m) Magnetic Field of Earth: 5.0 x 105 T 1 gauss = 1 G = 10-4 T

Relationships •Magnetic Field Lines: The direction of the magnetic field, B at given location is the direction in which the north pole of a compass points when placed at that location. •Magnetic field lines exit from the north pole of a magnet-and enter at- the south pole. •Magnetic field lines never cross. •Geomagnetism: The "north" magnetic pole of the Earth is usually the "south" pole of the Earth's magnetic field. Magnetic force depends on: (i) charge of particle q (ii) speed of the particle, v (iii) the magnitude of the magnetic field, B; and (iv) the angle between the velocity vector and the magnetic field vector, Θ. •A particle must have a charge and be moving in order for the field to exert a force on it. •The magnetic force F points in the direction that is perpendicular to both B and v. To find the direction of the magnetic force on a positive charge: 1.) Point your fingers in the direction of velocity. 2.) Curl your fingers toward the direction of B. 3.) Your thumb points in the direction of F. If the charge is negative, the force points opposite of the direction of your thumb.

CH 22 Magnetism Electric vs Magnetic Forces Constant -Velocity, Straight - Line Motion Circular Motion Helical Motion •Magnetic field does no work on a charged particle. •Speed of the particle in the magnetic field remains constant. •Simplest motion. •In such cases, the particle's accelerati on is zero, hence, its velocity remains constant. •Centripet al force is required to cause the motion. In this case, the centripeta l force is supplied by the magnetic force. Mv2/r=qvB r=mv/qB. •The faster and more massive

CH 22 Magnetism Magneti c Force Exerted on a CurrentCarrying Wire

Magneti c Force in a Long, Straight, Wire Current Loops and Solenoid s

Magnetic force is given by the same right hand rule used earlier for single charges. 1) Point fingers in the direction of I. 2.) Curl your fingers toward the direction of B. 3.) Your thumb, indicates the direction of F.

F=ILBsinΘ S.I. = N

1) Point your thumb along the wire in the direction of the current I. Your fingers are now curling around the wire in the direction of the magnetic field. Center of a Circular Loop B=Nµ0I/2R Magnetic Field of a Solenoid B=µ0(N/L)I=µ0nI S.I.= tesla, T

•Current loops with currents in the same direction attract. Solenoid: is an electrical device in which a long wire has been wound into a succession of closely spaced loops with the geometry of a helix.

Magnetic Force

Moving Charges Magnitude of the Magnetic Force, F F=qvBsinΘ S.I.=N Definition of the Magnitude of the Magnetic Field, B B=F/qvsinΘ S.I.= 1 tesla = 1 T = 1 N/A (A•m) Magnetic Field of Earth: 5.0 x 10-5T 1 gauss = 1 G = 10-4 T

Current Carrying Wire

Long, Straight, Wire

F=ILBsinΘ S.I. = N

1) Point your thumb along the wire in the direction of the current I. Your fingers are now curling around the wire in the direction of the magnetic field.

Right Hand Rule

Regular Magnetic Force

Long, Straight Wire

To find the direction of the magnetic force on a positive charge: 1.) Point your fingers in the direction of velocity. 2.) Curl your fingers toward the direction of B. 3.) Your thumb points in the direction of F.

1) Point your thumb along the wire in the direction of the current I. Your fingers are now curling around the wire in the direction of the magnetic field.

CH 22 Magnetism If the charge is negative, the force points opposite of the direction of your thumb.