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  • Michael Faraday

    who first demonstrated the principle of electromagnetic induction

    Electromagnetic induction

    producing current in a wire by placing it in a changing magnetic field

    wire&wire

    Either the ____ can move in the magnetic field or the field can move around the ____ - one or the other must move to induce current.

    -rotate a wire
    -drag a wire through magnetic field
    -move a magnetic field across a wire

    three ways to induce current

    emf

    Separation of charges by magnetic force will induce ____in the wire

    electrons

    The magnetic field force pushes the___ through the wire

    3rd

    Use the ___ right hand rule to figure out the direction of current flow in the wire

    -speed of wire or magnetic field motion
    -length of wire in the field
    -strength of magnetic field

    Magnitude of emf depends on (3):

    perpendicular

    Induced current is greatest if the wire and magnetic field are_____ to each other

    parallel

    if the angle is zero the wire is____ to the magnetic field

    perpendicular

    Only the portion of the magnetic field____ to the wire will induce current in it

    size & rotating

    Changing the ___ of the loops of wire or _____ the loop in the magnetic field will change the amount of induced current

    magnetic field

    The current induced in the wire by moving through a magnetic field will generate its own _______

    opposite

    As the magnetic field approaches the wire, the wire's magnetic field is in the____ direction of the increasing magnetic field

    bar magnet

    The induced magnetic field is similar to a _____- and creates a force that repels the original magnetic field

    same

    As the coil moves out of the magnetic field the induced field is in the_____ direction as the original and they attract each other

    lens law

    "The magnetic field of an induced current is in a direction to produce a field that oppose the change causing it"

    CHANGE

    The induced field does not oppose applied field, but the____ in the applied field

    induced field

    If the applied field changes, the _____ helps to keep it constant

    Faraday's Law of Induction

    Predicts the magnitude of induced emf

    Lenz's law

    tells the direction of the induced emf

    Equation for single loop

    emf = -∆ϕM/∆t

    emf from one loop

    When you have multiple loops, you multiple the number of loops (N) by the ____

    equation for multiple loops

    N∆ϕM/∆t

    volt (V)

    emf unit is the

    orientation

    Current can also be generated in a magnetic field by changing the_____ of the loop in the magnetic field

    mechanical energy

    Most power plants use a source of _____ to turn a turbine in a magnetic field to generate current.

    emf

    A generator produces changing____, because of its constant rotating

    0 emf

    when the armature is perpendicular to the magnetic field in a generator, you get____

    maximum emf

    when the armature is parallel to the magnetic field in a generator, you get ____

    AC current

    As the loop rotates from one arm being up to the other being up, the current flow will change direction - producing ____

    emf for generator (maximum)

    emf = NAβω

    ω

    is the angular speed of rotation of the loop (2πf)

    frequency

    The____ of rotation of the loop in a generator will determine how often the current changes direction -> f = 60Hz in US

    AC can be converted to DC

    add rings (slip rings) and brushes to the end of the loops, the moving rings counter the changing current and create direct current for a circuit

    motor

    convert electrical energy to mechanical energy

    permanent magnet

    Current is supplied to loops and that magnetic field repels ______ and causes the loops to rotate

    back emf

    The motor's magnetic field generates its own emf called ___

    Back emf

    ____ increases as the magnitude of the magnetic field changes at a higher rate

    potential difference

    The _____ supplied to the motor equals the applied emf minus the back emf, this also reduces current

    reduce

    As a motor turns more quickly, the net emf and net current in the coil___

    Mutual inductance

    ____ is the ability of one circuit to induce emf in a nearby circuit in the presence of a changing magnetic field

    Mutual inductance

    emf = - M(∆I/∆t)

    M

    __ depends on the shape of the coils and how they are orientated to each other

    M

    is the mutual inductance of the two-coil system

    number

    Changing the____ of coils in the secondary coil can change the induced emf in the secondary coil - used in making transformers

    emf & current

    Because AC current changes direction, the____ and____ in an AC circuit is not constant

    emf & current

    Effective ___ and effective ____ are the average values in the AC circuit - called Irms

    Ohm's Law

    You can use ____ to find resistance

    transformers

    A device that increases or decreases the emf of alternating current

    first coil called primary

    current in this coil magnetizes the iron core

    Second coil called secondary

    current runs through the 2nd coil because it is wrapped around magnetized iron

    Real transformers

    _____ are only 90-99% efficient - power is lost due to small currents induced by changing magnetic field and resistance in the wires

    transformer equation

    ∆V2/∆V1 = N2/N1

    Step-up transformer

    increases the emf, N2 is greater than N1

    Step-down transformer

    decreases the emf, N2is less than N1

    decrease

    The increase in emf means a____ in current

    increase

    An decrease in emf means an____ in current

    230 000V

    In the US, power companies step-up emf to about ____

    12V

    Car batteries provide a constant DC emf of ___

    The Ignition coil

    ____ in the engine is a transformer that increases this emf to a great enough value to cause a spark between the gaps of a spark plug

    electromagnetic waves

    Oscillating electric and magnetic fields create

    James Clerk Maxwell

    ____created a set of equations that explain the relationship between electric and magnetic fields

    electromagnetic in nature

    Maxwell predicted that light was ___-

    Heinrich Hertz

    ___performed experiments that generated and detected EM waves and confirmed Maxwell's predictions.

    transverse waves

    electromagnetic waves are ___

    right

    Oscillating Electric and Magnetic waves - at___ angles to each other

    single force

    Electric and magnetic forces are aspects of a ____ - called electromagnetic force

    inverse square law

    Electromagnetic force obeys the ____ - as the two objects move further apart the force between them weakens

    accelerating charges

    All EM waves are produced by ____ - a charge moves up/down through the wave at a certain frequency

    charged particular

    motion of _____ through a wave makes it move

    energy

    Electromagnetic waves transfer____ - stored in the oscillations of the electric and magnetic fields

    Electromagnetic Radiation

    Energy transported by EM waves is called ____

    particles

    Some high energy EM waves will behave like____

    wave-particle duality of light

    Notion that EM waves behave like particles is called the____

    photon

    A particle of light is called a____ - carries energy, but has no mass

    waves

    Low-energy photons behave more like ___

    particles

    High-energy photons behave more like____

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