EMF Theory

Describe Lorentz Force Law

• Force acting on a moving point charge, q in the presence of electro-magnetic fields

• F = qV x B

• F = q(E + V x B)

• States that the magnetic flux density near a long , conductor is directly proportional to the current in the conductor and inversely proportional to the distance from the conductor

Describe Ampere's Law

• 
• The magnetic force on a stationary charge or a charge moving in parallel to the magnetic field is zero

• 
• The magnetic field in space around an electric current is proportional to the current which produces it

What is Gauss' Law?

• 
• Enclosed charge is net charge

• Used to find magnetic field

• Used to find electric field

-An effective way of producing a magnetic field that is constant at its center

-Made of many loops of wire, packed closely together

The descriptions above best describes SOLENOID or TOROID?

• SOLENOID

• TOROID

• -Bent into the shaped of a doughnut

• -Uses Ampere's Law to find magnetic field in its interior points

The descriptions above best describes SOLENOID or TOROID?

• SOLENOID

• TOROID

Propose the solution for designing a supercapacitor with large capacitance.

• Use larger surface area for the plates

• Decrease the distance between plates

• Increase the input voltage

• Choose materials with larger dielectric constant

Describe the nature of EM waves in terms of the electric and magnetic fields that make up the waves.

• Since a changing electric field produces a magnetic field, and a changing magnetic field produces an electric field, once sinusoidal fields are created they can propagate on their own

• These propagating fields are called electromagnetic waves

• When electric field changes, magnetic field equals to 0

• The electric and magnetic waves are perpendicular to each other as they propagate through vacuum

-When a sinusoidal varying current is sent through the large transmitting coil C, the coil produces a continuously varying magnetic field in its vicinity.

-If a conductor, such as a buried gold coin, lies nearby, the magnetic field induces a continuously varying current in that conductor.

-The continuously varying current in the conductor produces its own varying magnetic field, which induces current in the receiving coil of the detector and signals the presence of the coin or other conductor being detected.

Which Law states the explanation above?

• Faraday's Law

• Coulomb's Law

• Gauss' Law

• Ampere's Law

How to magnetize and demagnetize a magnetic material?

• Magnetize - An unmagnetized bar is placed in a magnetic field and when the field is removed the bar is magnetized; motion of electric charge create magnetic field

• Magnetize - When a random plate of metal is placed close to a magnet

• Unmagnetized - The magnetic materials can be heated or striked with a large force

• Unmagnetized - Chop the magnetic materials into pieces

Lenz's Law states that;

• Changing the rate of rotation will change the output emf frequency

• The induced current in a closed conducting loop will flow in such a

  direction that its flux opposes the change that produces it

• Represented by the minus sign in Faraday's Law

• The induced electromotive force or EMF in any closed

  circuit is equal to the time rate of change of the magnetic flux through the

  circuit.