The Movement of Charged Particles in a Magnetic Field By Emily Nash And Harrison Gray

Preview Magnetic fields and their poles Magnetic field of the earth Solar wind and how the earth’s magnetic field affects it Taking a look at the force that magnetic fields exert upon electrons by using a cathode ray tube, magnets, and some simple math.

Magnetic Fields N S Magnetic Fields are created by moving charged particles, and only affect moving charged particles. Forces between two electric currents is what causes a magnetic force. Two parallel currents flowing in the same direction repel each other, while two parallel currents flowing in opposite directions repel each other. N When there exists a steady stream of electrons, a negatively charged particle, an electric current forms, which produces a magnetic field. This force leads to the idea of the north and south poles of a magnetic field. S

Magnetic Poles

Earth's Magnetic Field N S The Earth itself is a magnet, with a magnetic north pole and south pole. The origin of the Earth’s magnetic field is said to be a result of the dynamo effect, electric currents produced by the rotation of the iron-nickel core. N The Earth’s magnetic field continually traps moving charged particles coming from the sun. S High concentrations of these particles within the field are called the Van Allen Radiation belts. These particles are called cosmic rays, which originally come from the sun.

Solar Wind Magnetotail Bow Shock Magnetosheath Solar Wind consists of gases comprised of protons, electrons, and ions which hurl towards the earth from the sun at velocities of 450 km/sec or higher. Bow Shock The path of these particles change almost directly as they hit the earth’s magnetosphere at the region called the bow shock. Magnetosheath The impact of the solar wind causes The field lines facing the sun to compress, While the field lines on the other side stream back to form a Magnetotail. Because the charged particles of the rays are deflected around the magnetosheath, the earth is protected from most of the deadly radiation.

contribute to the Van Allen radiation belts. Solar Wind Cntd Some solar wind particles, however, do escape the earth’s magnetosphere and contribute to the Van Allen radiation belts. When these particles do enter the magnetic field, they go through three motions: Spiral- the magnetic field changes the path of the particle. The particle, in its new path, is still deflected by the field, and therefore takes a spiraling motion around a magnetic field line. Bounce- the particles eventually bounce towards the opposite pole, where they spiral again. Drift- as the particle continually spirals and bounces, it drift around the magnetic field and is trapped in the magnetosphere. In order to better understand the motion of particles through a magnetic field, we have conducted an experiment involving creating an electron beam and running it through magnets as a parallel to solar wind entering the earth’s magnetic field.

√ Cathode Ray Tube Cntd. Since change in energy is the voltage times the charge then ½mv²=qV Therefore v= √(2qV/m) The potential energy of electrons is converted to kinetic energy Electrons are attracted to positively charged plate. They accelerate towards it and small percentage escape the plate through small hole, creating electron beam. 120 Volts Plate is heated and electrons boil off. Velocity= 0 Potential Energy= ½ mv^2 6.3 Volts

Cathode Ray Tube

Calculating the Velocity of the Electrons We now know that v= √(2qV/m), so we can now easily find the velocity of our beam of electrons. q(charge) of an electron= -1.6•10^-19 V(volts)=120 m(mass) of an electron=9.11•10^-31 Therefore: v=√(2)(-1.6•10^-19)(120)/(9.11•10^-31) v=√4.215•10^13 v=6492417.261 m/s

therefore the electron Bending Electron Beams Like Solar Wind, the electrons in the CRT beam are deflected when entering a magnetic field, therefore the electron beam “bends.”

Bending Electron Beams In order to predict the angle at which the electrons are deflected, we must first measure the force that the magnetic field inserts upon the beam Since acceleration is equal to v²/r we can deduce that F=m(v²/r) To do this, we use the equation: F=ma according to Newton’s second law

Calculating the Force of the Magnetic Field We now know that F=m(v²/r), so we can use this formula to find the force that the magnetic field exerts upon the electrons. mass= 9.11•10^-31 velocity= 6492417.261 m/s And we measured the distance of the electron beam from the magnets to be .075 meters Therefore F= 9.11•10^-31(6492417.261²/.075)