Magnetic Flux Density, Reluctance, and Permeability Concepts

Electrical Energy Production

• Triboelectricity is the method of producing electrical energy that involves the friction between moving objects.
• Piezoelectric crystals produce a voltage when subjected to pressure.
• Photovoltaic cells convert radiant energy to electrical energy.
• Thermocouples utilize the principle of Seebeck effect.

Electromagnetic Induction

• A changing magnetic field produces a voltage in electromagnetic induction.

Units and Quantities

• The SI unit for resistance is the ohm (Ω).
• James Watt is known for the development of the unit 'Watt'.
• The symbol 'E' in the equation E = IR represents electromotive force.
• The SI unit of conductance is the siemens (S).
• Charles-Augustin de Coulomb is associated with the unit 'Coulomb'.
• The unit of power in the cgs system is the erg per second.

Magnetic Circuits

• Magnetic flux density is the measure of the magnetic field's strength at a given point.
• Reluctance is defined as the opposition to magnetic flux in a magnetic circuit.
• Permeability is analogous to conductivity in magnetic circuits.
• The magnetic field force produced by a current-carrying wire can be increased by increasing the current or the number of turns of the wire.
• The right-hand rule indicates that the magnetic force on a current-carrying wire is perpendicular to the direction of the current and the magnetic field.
• The magnetic dipole moment μ of a current loop points in the direction perpendicular to the loop and through its center.

Lighting Levels

• The lighting level for the cow's udder in the dairy milking operation area is 50 footcandles.
• The lighting level for egg processing is 100 footcandles.
• The lighting level for machine storage, garage, and machine shed is 20 footcandles.
• A lighting level of 1080 lux is found in the dairy milking operation area.
• The lighting level in the feeding area in the dairy milking operation is 540 lux.

Electrical Circuits

• A maximum of 12 outlets are recommended for each 15 A circuit.
• A lighting level of 750 lux is found in the dairy milking operation area.
• The general load assumed for each small appliance circuit in a residence is 2 amps.
• For a residence with 70 outlets, 5 circuits are needed if all are 15-A circuits.
• The factor used for all floor areas excluding specific spaces is 1.5.
• For a residence with 60 outlets, 2 20-A circuits and 2 15-A circuits are recommended.
• The outside dimension of the two-storey house mentioned in Example 22 is 40 ft x 30 ft.