Physics- Chapter 23 and 24 PDF

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Physics- Chapter 23 and 24 Notes...

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Current topic:

Electromagnetic Induction and Electromagnetic Waves

Chapters Chapter 23.1 – 23.3, 23.5, and 23.7 Textbook: Chapter 24.1 – 24.3 Name *Describe IYOW Concepts 1 Induction Basic process of generating electromotive force and currents with Summary: magnetic fields Also known as Magnetic Induction 2 Farraday’s The apparatus used by Faraday to demonstrate that magnetic fields Apparatus can create currents

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Electromagnetic Consist of oscillating electric and magnetic fields and propagate at Waves the speed of light Magnetic Flux Φ = BAcosθ Φ= B ⊥ A Bcosθ = B ⊥ B = Magnetic Field The component of B Strength perpendicular to the A = Area area (A) θ = Angle perpendicular to the area Units: T ⋅ m 2 Electromagnetic Any change in magnetic flux Φ induces an EMF Induction

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Faraday’s Law of Induction

 EMF is directly proportional to the change in flux ΔΦ  EMF is greatest when the change in time Δt is smallest (EMF is inversely proportional to Δt)  If a coil has N turns, an EMF will be produced that is N times greater than for a single coil, so that EMF is directly proportional to N. ΔΦ BΔA lΔx EMF = EMF = B EMF = -N Δt Δt Δt

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Lenz’s Law

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Magnetic Force

A law stating that the direction of an induced current is to oppose the change in the circuit or the magnetic field that produces it. F=qvBsinθ moves in the opposite charges in opposite directions and produces EMF = Bℓv

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Velocity

Δx Δt

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Electric Generators EMF Induced In A Generator Coil Frequency Of The Oscillation

Induce an EMF by rotating a coil in a magnetic field EMF = EMF 0 sinωt Maximum (peak) EMF f=

EMF = NABωsinωt

ω 2π

The number of waves that pass a fixed point in unit time

1 f

2π ω

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Period

1 3

Angular Velocity

ω = Δt

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Transformers

They transform voltages from one value to another; they also have internal resistance.

15 Two Type of Coils

T=

= Δθ

The two coils are called the primary and secondary coils. The input voltage is placed on the primary. The secondary produces the transformed output voltage. ΔΦ Δt Ns Np

EMF = - N p 1 6

Transformer Equation

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Step-Up Transformer

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Step-Down Transformer

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Relationships Between Inputs and Outputs

2 0

Maxwell’s Equations

2 1

Heinrich Hertz

Vs Vp

=

The ratio of the secondary to primary voltages in a transformer equals the ratio of the number of loops in their coils Increases voltage

Decreases voltage

P p=I p V p=I s V s= P s

Vs Vp

=

Ip

Is

Is

Ip

=

Np Ns

 Gauss’ Law for electric fields  Gauss’ Law for magnetism Maxwell concluded that light is an electromagnetic wave.  First to generate and detect certain types of electromagnetic waves in the lab  Used an AC RLC (resistor-inductor-capacitor) circuit  Prove that electromagnetic waves travel at the speed of light

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 v =f λ Electromagnetic Whenever a current varies, associated electric and magnetic fields Waves vary, moving out from the source like waves.

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Amplitude

The maximum extent of a vibration or oscillation, measured from the position of equilibrium

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Wavelength

Equals the distance between two successive wave crests or troughs

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Transverse Wave

They are perpendicular to one another and to the direction of propagation

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Standing Wave

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Resonant

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Light

 Also called stationary wave  Combination of two waves moving in opposite directions, each having the same amplitude and frequency. Occurs when the frequency of a periodically applied force is in harmonic proportion to a natural frequency of the system on which it acts. E c= B E = E-Field Strength B = B-Field Strength c = Speed of Light (3 × 108 m/s)

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Electromagnetic Spectrum: Rules Of Thumb

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Radio Waves

An electromagnetic wave of a frequency between about 104 and 1011 or 1012 Hz

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Extremely Low Frequency (ELF)

A radio frequency in the lowest range of the radio spectrum.

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Amplitude Modulation

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Carrier Wave

The modulation of a wave by varying its amplitude, used in radio broadcasting, where an audio signal is combined with a carrier wave. A high-frequency electromagnetic wave modulated in amplitude or frequency to convey a signal.

 High-frequency electromagnetic waves are more energetic and are more able to penetrate than low-frequency waves.  High-frequency electromagnetic waves can carry more information per unit time than low-frequency waves.  The shorter the wavelength of any electromagnetic wave probing a material, the smaller the detail it is possible to resolve.

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Frequency Modulation

The modulation of a radio or other wave by variation of its frequency, especially to carry an audio signal.

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Very High Frequency

Frequencies between 30 and 300 megahertz used for broadcasting television signals

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Ultra High Frequency

Radio frequency in the range 300 to 3,000 MHz.

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Microwaves

An electromagnetic wave with a wavelength in the range 0.001–0.3 m

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Thermal Agitation

Random movements of the free electrons in a conductor, producing noise signals.

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Radar

A system for detecting the presence of objects by sending out pulses of high-frequency electromagnetic waves.

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Infrared Radiation

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Visible Light

Portion of the electromagnetic spectrum that extends from the long wavelength, or red, end of the visible-light range to the microwave range Wavelengths that are visible to most human eyes

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Ultraviolet Radiation

A wavelength greater than 100 nm but less than 400 nm.

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X-Ray

An electromagnetic wave of high energy and very short wavelength, which is able to pass through many materials opaque to light

Gamma Rays

Penetrating electromagnetic radiation of a kind arising from the

radioactive decay of atomic nuclei. Problems Worked:

Chapter 23: Problems & Exercises: 1-6, 8, 9, 17, 20, 29, 47

Chapter 24: Problems & Exercises: 12, 13 and 16  Magnetic flux is Φ=BAcosθ. **Context Summary:  Faraday’s law of induction states that the emf induced by a change in magnetic flux is emf=−NΔΦΔt.  EMF = Bℓv  Electromagnetic waves consist of oscillating electric and magnetic fields and propagate at the speed of light. They are created by oscillating charges .  Equations: Gauss’s law for electricity, Gauss’s law for magnetism, Faraday’s law of induction, including Lenz’s law, Ampere’s law  c = fλ  The different types of electromagnetic radiation shown in the electromagnetic

spectrum consists of radio waves, microwaves, infrared waves, visible light, ultraviolet radiation, X-rays, and gamma rays....