Electromagnetics

Electromagnetics

by Ronnie Lorilla

Electromagnetic Induction

We know an electric current can be induced by a magnetic field

• Is it possible to do the reverse?

• Is it possible to use a magnetic field to generate an electric current?

• Answer: Yes!

Electromangetic induction

• Electromagnetic induction is the process of inducing a current in a circuit by changing the magnetic field that passes through the circuit

• In electromagnetic induction, a changing magnetic field induces a current

Michael Faraday

British scientist, 1791-1867

Multiple Choice

Electromagnetic induction is...

• The process in which a current produces a magnetic field

• The process in which a changing magnetic field generates electricity

• The process in which electricity is produced by connecting wires to a battery

• The process in which lightning strikes a building

Multiple Choice

Which of the following will generate a current in a loop?

• A magnet

• A gravitational force

• A moving magnet

• Friction

Multiple Choice

Who discovered electromagnetic induction?

• Isaac Newton

• Benjamin Franklin

• Hans Oersted

• Michael Faraday

Wave Equations

Wave Speed (v) = Distance (x) / Time (t)

Wave Speed (v)(m/s) = frequency (f)(Hz) x Wavelength(m)

Multiple Choice

What is the correct equation for calculating Wave Speed

• Distance / Wave Length

• Time / Distance

• Frequency x Wave Length

• Distance x Time

Multiple Choice

Velocity= 600 m/s

Wavelength= 2.0m

Frequency= _________

• 300 hertz

• .0033 hertz

• 3000 hertz

Multiple Choice

Velocity= ________

Wavelength= .5m

Frequency= 150 hertz

• .75 m/s

• 75 m/s

• 300 m/s

Multiple Choice

A wave has frequency of 50 Hz and a wavelength of 10 m. What is the speed of the wave?

• 500 m/s

• 50 m/s

• 5 m/s

• 0.5 m/s

Multiple Choice

What is the speed of a wave with a wavelength of 10m and a frequency of 2 kHz?

• 200m/s

• 20,000 m/s

• 20 m/s

• 0.2 m/s

Transverse

e.g. a water wave, objects will bob up and down and the wave passes.

Longitudinal

e.g tuning fork in air, you don’t get a vacuum by the side of the tuning fork.

Both transfer energy. The wave travels and not the medium.

Multiple Select

Select the transverse waves.

• water waves

• light

• ultrasound

• radio waves

• P waves

Multiple Choice

Sound waves can travel through a vacuum because they don't require particles.

• True

• False

electromagnetic waves

Timeline in the Development of Electromagnetic waves

• Alessandro Volta

• Hans Christian Oersted

• Andre Marie Ampere

• Michael Faraday

• James Clerk Maxwell

• Heinrich Hertz

Alessandro Volta (1745-1827)

Italian physicist known especially for the development of the first electric cell in 1800.

Hans Christian Oersted (1777-1851)

Danish physicist and chemist. He discovered electromagnet. He discovered that electric current generates magnetic field.

Andre Marie Ampere (1775-1836)

French physicist and mathematician. He investigated electric current and electrodynamics. His most significant contribution was the mathematical formulation of magnetism, known as Ampere Law in 1827.

Michael Faraday (1791-1867)

English chemist and physicist. He discovered the laws of electrolysis and electromagnetic induction and described his life's work in Experimental Researches on Electricity.

James Clerk Maxwell (1831-1879)

One of the world's greatest theoretical physicists. Maxwell's most important work was on the theory of electromagnetic radiation. He also formulated the kinetic theory of gases.

Hienrich Hertz (1857-1894)

German physicist, discovered electromagnetic waves and found they behave like light waves except for the wavelength. He was reputedly the first man to broadcast and receive radio waves and unit of the frequency was named after him.

Electromagnetic waves or EM waves

waves that are created as a result of vibrations between an electric field and a magnetic field

Transmission and propagation of EM waves

The transmission of electrical energy by wires, the broadcasting of radio signals, and the phenomenon of visible light are all examples of the propagation of electromagnetic energy. Electromagnetic energy travels in the form of a wave.

common properties of EM waves

• moving waves carry energy

• transverse waves

• travel in the same speed 3 x 10^8 m/s through vacuum

• can be reflected, refracted, or diffracted

Multiple Choice

Which electromagnetic radiation has the highest penatrating ability and is emitted only during high-energy nuclear reaction?

• gamma rays

• microwave radiation

• radio waves

• x-rays

Multiple Choice

Which is true about electromagnetic waves?

• All travel at the same speed.

• All have the same frequency.

• All have the same wavelength

• All transport energy but not momentum

Multiple Choice

Which among the electromagnetic waves are emitted by hot objects?

• infrared rays

• microwaves

• radio waves

• x-rays

Multiple Choice

Which of the following do EM waves transport?

• electric charge

• energy

• frequency

• wavelength

Multiple Choice

The waves with the longest wavelengths in the electromagnetic spectrum

• Infrared rays

• gamma rays

• radio waves

• X-rays

Multiple Choice

Which of the following describes the height of a transverse wave?

• frequency

• trough

• crest

• amplitude

Multiple Choice

When all the waves of visible light are seen together, they make black light.

• True

• False

Multiple Choice

When all the waves of visible light are seen together, they make black light.

• True

• False

Multiple Choice

Xrays and Gamma Rays have the highest frequencies, therefore, highest energies.

• True

• False

Multiple Choice

All forms of radiation are harmful.

• True

• False