Magnetism Physics Laycott – Flashcards
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Like poles
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repel
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Magnet poles ___ be isolated
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cannot
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If you cut a magnet in half
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You get two smaller magnets
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If you keep chopping up a magnet, you will eventually reach a minimum size, below which the pieces cease to be magnets.This is called
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A Magnetic Domain
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__are magnetic at the microscopic level
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Permanent Magnets
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__are those that can become strongly magnetized, such as iron and nickel
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Ferromagnetic materials
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Ferromagnetic materials are made up of tiny regions called domains; the magnetic field in each domain is
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in a single direction
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Magnetic data storage
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store information as a microscopic pattern of magnetic domains which can be magnetized to write data, and measured to read the data.
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The Earth's Magnetic field Strength
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BEarth = 0.5 x10-4 Tesla
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The Earth's Magnetic field Generated by
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circulating currents in the Earth's molten iron core
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__showed that ALL magnetic fields are due to moving charges
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Einstein
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Magnetic fields are a consequence of
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Special Relativity
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Conductor w/ no current
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no net charge
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right hand grip thumb is
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current
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rught hand grip pointer is
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field
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right hanf grip middle is
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force
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A positive charge enters a uniform magnetic field as shown. What is the direction of the magnetic force?
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to the left
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Symbol for Magnetic Field/Units
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B/Tesla
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This equation defines the magnetic field
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F=IlBsin(0) at right angle F=IlB
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A positive charge enters a uniform magnetic field as shown. What is the direction of the magnetic force?
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upwards
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A positive charge enters a uniform magnetic field as shown. What is the direction of the magnetic force?
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into the page
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If a charged particle is moving perpendicular to a uniform magnetic field, its path will be
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a circle.This happens because the magnetic force points at right angles to the particle's direction of motion.the particle feels a centripetal force.
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Atoms are neutral objects whose net charge is zero thus,
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they do not experience a magnetic force.
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A proton enters a uniform magnetic field that is perpendicular to the proton's velocity. What happens to the kinetic energy of the proton?
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it stays the same. The velocity of the proton changes direction but the magnitude (speed) doesn't change. Thus the kinetic energy stays the same.
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current PRODUCES s B-field, how to calculate it:
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B=u/2pi x I/r u=constant
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Parallel currents
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attract
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antiparallel currents
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repel
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All Magnetic Fields are due
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to electric charges in motion
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___ is a long coil of wire. If it is tightly wrapped, the magnetic field in its interior is almost ___
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A solenoid/Uniform
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Soleniod formula
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B=uIN/l
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____:a piece of iron is inserted in the solenoid, the magnetic field greatly_
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electromagnets/increases
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An electric motor also takes advantage of___, to change electrical energy to mechanical energy.
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torque on a current loop
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Loudspeakers use the principle that a magnet exerts a force on a current-carrying wire
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to convert electrical signals into mechanical vibrations, producing sound.
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A magnet moving near a conductor (a wire or a coil of wire) causes an electric current to flow called
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induction
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A _____consists of two coils, either interwoven or linked by an iron core. A changing emf in one induces an emf in the other.
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transformer
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Transformer ratios
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Vs/Vp=Np/Ns N=number of turns
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Transformers work only if__,this is one reason why electricity is transmitted as__
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if the current is changing/AC
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___will interrupt the current to a circuit that has shorted out in a very short time, before a dangerous current flows, preventing electrocution.
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A ground fault circuit interrupter (GFCI)
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GFCI:Anti-parallel currents produce opposite magnetic fields, so a short distance away from the wires, there in
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NO NET Magnetic Field.If even a tiny current leaks out of the device (say to your wet finger as you reach for a hair dryer), the incoming and outgoing currents become imbalanced. a second coil opens a switch.
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it transforms mechanical energy into electrical energy.
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A generator
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Generators that use magnets and coils, plus a source of mechanical power are often called
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Alternators (the simplest and most efficient type of generator.)
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Alternators produce
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alternating current
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is induced in each coil in the generator
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A sinusoidal emf
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The frequency of the AC waveform depends on
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how fast the generator rotates
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A generator has a coil of wire rotating in a magnetic field. If the rotation rate increases, how is the maximum output voltage of the generator affected?
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increases
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__has a fixed coil and a magnet hung on a spring (or vice versa), and records the current induced when the earth shakes.
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A seismograph
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The magnetic force is __to the magnetic field direction.
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perpendicular
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In order to change the magnetic flux through the loop, what would you have to do?
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Since Φ = B A cosθ , changing the area or tilting the loop (which varies the projected area) would change the magnetic flux through the loop
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An electron is traveling horizontally toward the north in a uniform magnetic field that is directed vertically downward. In what direction does the magnetic force act on the electron?
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east
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A charged particle enters into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle's weight, what type of path will the particle follow?
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The charged particle will follow a circular path.
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The magnitude of the magnetic field at a certain distance from a long, straight conductor is represented by B. What is the magnitude of the magnetic field at twice the distance from the conductor?
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At twice the distance, the magnitude of the field is B/2
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Two long parallel wires are placed side by side on a horizontal table. The wires carry equal currents in the same direction.the following statements are true...
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The magnetic force between the two wires is attractive. The magnetic field at a point midway between the two wires is zero.
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How strong is the magnetic field 2.5cm from one cable?
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B = (Uo)I / 2pi*r
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What current would the wire carry?
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Fb=Fg ILB=mg IkB=2 pi (d/2)^2 g (density copper)
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the following will produce a magnetic field
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The Earth. An electric current. A magnet. A moving electric charge.
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When a charged particle moves parallel to the direction of a magnetic field, the particle travels in a
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straight line.
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As a proton moves through space, it creates
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both an electric field and magnetic field.
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the following statements about the force on a charged particle due to a magnetic field are all valid
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It depends on the strength of the external magnetic field. It acts at right angles to the direction of the particle's motion. It depends on the particle's velocity. It depends on the particle's charge.
