19.1 Magnets, Magnetic Poles, and Magnetic Field Direction How does a compass work? –The north pole of a compass needle was defined as North Pole Seeking. (That is the end will point towards North on Earth.) –Confusing result of history! North pole of compass is… MIND BLOWN!!!!
19.1 Magnets, Magnetic Poles, and Magnetic Field Direction A magnet creates a magnetic field: The direction of a magnetic field (B) at any location is the direction that the north pole of a compass would point if placed at that location. (This is very similar to the electric field.)
19.2 Magnetic Field Strength and Magnetic Force Let’s watch a little video on the right hand rule. Now let’s do some practice with this. Right Hand Rule PracticeRight Hand Rule Practice
19.2 Magnetic Field Strength and Magnetic Force Conceptual Example: –In a linear accelerator, a beam of protons travels horizontally northward. To deflect the protons eastward with a uniform magnetic field, which direction should the field point: A) Vertically downward B) West C) Vertically upward D) South
19.2 Magnetic Field Strength and Magnetic Force A particle with a charge of - 5.0 x 10 -4 C and a mass of 2.0 x 10 -9 kg moves at 1.0 x 10 3 m/s in the positive x direction. It enters a uniform magnetic field of 0.20 T that points in the +y direction. A) Which way will the particle deflect as it enters the field? B) What is the magnitude of the force on the particle when it is in the field? C) What is the radius the particle will travel?
19.4 Magnetic Forces on Current-Carrying Wires Because a current-carrying wire is acted on by a magnetic force, it would seem possible to suspend such a wire at rest above the ground using Earth’s magnetic field. –A) Assuming this could be done, consider long, straight wire located at the equator. What would the current direction have to be? U/D/E/W –B) Calculate the current required to suspend the wire, assuming Earth’s magnetic field is 0.40 Gauss at the equator and the wire is 1.0 m long with a mass of 30 g.
19.6 Electromagnetism: The Source of Magnetic Fields The maximum household current in a wire is about 15 A. Assume that this current exists in a long, straight, horizontal wire in a west-to-east direction. What are the magnitude and direction of the magnetic field the current produces 1.0 cm directly below the wire?
19.6 Electromagnetism: The Source of Magnetic Fields What your test will most likely do is ask you for the formula in a multiple choice question. Which means you must memorize the formula because I will test you on this with multiple choice questions!
19.6 Electromagnetism: The Source of Magnetic Fields A solenoid is 0.30 m long with 300 turns and carries a current of 15.0 A. –A) What is the magnitude of the magnetic field near the center of this solenoid? –B) Compare this with the result from the last example with a long straight wire.
19.6 Electromagnetism: The Source of Magnetic Fields Two long, parallel wires carry currents in the same direction. –A) Is the magnetic force between these wires attractive or repulsive? –B) Wire 1 carries a current of 5.0 A and the current in wire 2 is 10 A. Both have a length of 50 cm, and they are separated by 3.0 mm. Determine the magnitude of the magnetic field created by each wire. –C) Determine the magnetic force that each wire exerts on the other.