p6 Q4

electromagnetic induction

Generation of electromotive force or voltage across an electrical conductor in a changing magnetic field

Michael faraday Sep 22, 1791

A british scientist who studied electricity and magnetism; discovered electromagnetic induction; his work led to generators and electric power

Faraday's law

Explains how electricity is created by changing magnetic fields; when the magnetic field changes near a coil of wire it makes electricity flow

Electromotive force

The electrical push that causes charges to move in a circuit; it makes a current flow (switch on)

Epsilon ε and Volts V

Symbol and unit of electromotive force

Magnetic flux

Total amount of magnetic field passing through a given area; if it changes it induces electro motive force in a nearby conductor

Phi ϕ and weber wb

Simple and unit of magnetic flux

ϕ = BAcosθ

Formula for magnetic flux

Induced electromotive force

Electromotive force generated in a conductor when the magnetic flux changes; caused by moving coil, changing magnetic field, or changing coil area; generates an induced current if the circuit is closed

Induced current

Actual flow of electrons in the conductor caused by a changing magnetic field; it requires a closed circuit changing magnetic flux

Resistor

Keeps the current study or constant; closing the switch causes a sudden change in current which creates a changing magnetic field

ε = -N∆ϕB ÷ ∆t

Formula for electromotive force

I = ε ÷ R

Formula for induced current

P = I²R

Formula for power

6.25 × 10¹⁸ e-

Value of one ampere

1.6 × 10 -¹⁹ C

Value of one coulomb

Color perception

The ability of the human eye to distinguish different wavelengths of light as colors a complex process involving eyes brain and light

Electromagnetic wave

Made of vibrating electric and magnetic fields these fields travel together and carry energy

Transverse waves

Electric and magnetic fields vibrate at right angles of each other both are also perpendicular to the direction of wave travel therefore em waves are

300,000 km/s

All electromagnetic waves travel at the speed of _, slowest in solids and fastest in gases

v = lf

wave equation

Electromagnetic spectrum

Continuum of electromagnetic waves arranged according to frequency and wavelength is the gradual progression from lowest frequency to highest frequency

Correct sequence of the electromagnetic spectrum

Radio micro infrared visible ultraviolet x-ray gamma

6.63 × 10^-34

planck's constant

E = hf

energy equation

Radio waves

Longest wavelengths with the lowest frequency and energy produced by oscillating electric currents in antennas used in communication systems and discovered by heinrich hertz

Microwaves

Shorter wavelength than radio waves but higher frequency and energy absorb strongly by water molecules

Infrared waves

Invisible em radiation associated with heat emitted by all objects with temperature above absolute zero wavelength is longer than visible red light

Visible light

Only portion of electromagnetic spectrum visible to the human eye with wavelength ranging from 400 nanometers to 750 nm produced when excited electrons drop to lower energy levels

Ultraviolet rays

Located just beyond violet light higher frequency and energy than visible light can cause chemical changes in materials and living tissue

X-rays

Very high frequency and energy but very short wavelength highly penetrating electromagnetic waves produced when high speed electrons are suddenly decelerated named by wilhelm rowentgen

Gamma rays

Highest frequency and energy and lowest wavelength produced in nuclear reactions and radioactive decay extremely penetrating

Horseshoe magnet

a u-shaped magnet

Bar magnet

a vertical magnet

Magnet

a metal that attracts other metals

Magnetic resonance imaging

uses powerful magnetic fields to generate a radar-like radio signal from inside the body creating a clear detailed picture of bones organs and other tissues

dipole

every magnet has 2 poles, hence being:

monopole

unlike electric fields, its impossible to have a:

magnetic field

This is the region around a magnet where the magnetic force exists. Its lines exit from north and enter south poles

Tesla T

Strength of the magnetic field B

4π ⨯ 10⁻⁷ Tm/A

μ₀

Ampere

current I

μ₀ ⨯ I / 2πR

B

μ₀ ⨯ I / 2πB

R

2πRB / μ₀

I

north in, south out

when R is to the right

north out, south in

when R is to the left

ILBsinθ

strength of magnetic force