Phys 202 1nd Edition Lecture 12Outline of Last Lecture I. Solving problems using Kirchhoff’s lawOutline of Current Lecture II. MagnetismIII. Gauss’s Law of magnetostaticsIV. PolesV. Calculating magnetic fieldCurrent Lecture Magnetism:Magnetism is the oldest known force to humanity, known as a force even before gravity. When a magnet is suspended freely, one part of the magnet always points to the north and the other to the south. Therefore, magnets always have a north pole and a south pole. This is true no matter how small a magnet is or where is broken. This means that there is no such thing as a monopole magnet, or a strictly north or south magnet. Magnets also attract other materials like iron and nickel.Gauss’s law of magnetostatics:A magnet is surrounded by a magnetic field, very similar to how a charge is surrounded by an electric field. Magnetic field can be thought of as originating from the north pole and terminating at the south pole. This means that if you take a magnet, no matter how small, and surround it with a volume of any shape, for every magnetic field line that is leaving the object from the magnet, there is another magneticfield line moving in to the object and terminating at the magnet. Magnetic field is referred to as “B” and the unit is Tesla. The magnetic field of Earth(B) is roughly 10-5T.The amount of magnetic field lines, or magnetic flux, that moves through a surface is the surface integralof the normal component of the vector of magnetic field (B). This is described as;Φ=∫sB . dSWhich, since there is no such thing as an isolated monopole magnet, would be equal to zero. Because magnetic fields have no source or sinks and are magnetic field lines are continuous, we can also write this equation as;These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.∮s❑B .dS=∮∇ BvS=0This is known as Gauss’s law of magnetostatics.Poles:Similarly to charges and electric field, like poles on a magnet repel one another and opposite poles attract one another. Even within a spherical magnet, there will be a north pole charge and an opposite south pole charge. Earth Geographic North S N Geographic SouthImagine a giant magnet in the earth’s core. The south pole of the magnet faces the geometric north. Therefore, the north pole of a smaller magnet will point towards the south pole of the giant magnet, which would be the geometric north of Earth.Calculating magnetic field:The force(F) of a magnetic field (B) on a charge (q) moving with a velocity (v) can be represented by the equation;F=q(vxB)(vxB) means that the force on the moving particle is calculated as a cross product of the velocity of the particle and the strength of the magnetic field. To find the direction of the velocity and the magnetic field, you would use the “right hand rule”. Essentially, if you point your fingers in the direction of the vector v and curl them back in the direction of your vector B, your thumb should point straight out in thedirection of the vector (vxB). However, if q has a negative value, then the direction of the force vector will be opposite of the direction you get from the right hand rule.Alternately, if the angle (θ) between the vector v and the vector B is known, then you can ignore the right hand rule and solve for the force of the magnetic field on the charge with the equation;F=qvBsin(θ)Notice that, as we are using sin of θ, the velocity vector and the magnetic field vector can never be parallel to one