Some General Chemical and Electrical Terminology

• A unit of electrical current. One volt across a one ohm resistance causes a current to flow of one ampere.
• The rate of flow of electrons. One coulomb per second equals one ampere. Also, a current flow that deposits silver at the rate of 0.001118 grams per second equals one ampere.

• A component that stores electric charge.
• Two conductors separated by an insulator (dielectric).
• A capacitor is an open circuit to direct current.

• The capacitative reactance (opposition to the flow of ac current in a capacitor) decreases with increasing capacitance and increasing frequency.
• The formula for capacitative reactance is:
  
  
X_C = 1/6.283 fc

• f is the frequency
• c is the capacitance

• AC current leads the applied emf (electromotive force) by 90^o.
• AC voltage lags the current: negative reactance.

• A power supply where the output current stays constant, within limits, across changes in input voltage, temperature, or load resistance..
• The output voltage is adjusted to maintain the constant current condition.

• A power supply where the output voltage stays constant, within limits, across changes in input voltage, temperature, or load resistance..
• The output current is adjusted to maintain the constant voltage condition.

• The practical unit of electricity.
• A rate of flow of electrons of one ampere per second.

• The electric component of an electromagnetic field, abbreviated E-Field.
• The electric field and magnetic fields are associated with the movement of electrons through a conductor.
• The electric field and magnetic fields are mutually perpendicular.
• Electric fields are measured with a rod antenna.
• Electric fields are blocked by familiar materials, such as aluminum foil.

• The electric field setup by a stationary electric charge.
• An electrocstatic field cannot exist inside a closed metal container.
• An electrically continuous, conductive enclosure used for electrostatic shielding is known as a Faraday cage.

• The practical unit of magnetic induction: the force a magnetic field exerts on a single electron.
• Gauss are measured in maxwells/cm².
• One gauss is one line of flux (one maxwell) per square centimeter.

• The lag between the application of a magnetizing force and the development of magnetism in the material exposed to the force.
• As the magnetizing force, (H, expressed in oersteds) increases, the flux density (B, expressed in gauss) induced in the material being magnetized also increases.
• When an increase in H no longer produces an increase in B, the material is said to be magnetically saturated.
• If the magnetizing force H is reduced to zero, B diminishes by does not return to zero. This lag of B behind H is magnetic hysteresis.
• The amount of magnetism in the remaining when H reaches zero is known as residual magnetism .
• To reduce the remaining magnetism to zero, a negative magnetizing force, -H, must be applied. This force is known as the coercive force. See the figure.

• A component that opposes the flow of ac current.
• A conductor wound into a coil.
• An inductor is a short circuit to direct current.

• The inductive reactance (opposition to the flow of ac current in an inductor) increases with increasing inductnce and frequency.
• The formula for inductive reactance is:

where:

• f is the frequency
• L is the inductance

• AC current lags the applied emf (electromotive force) by 90^o.
• AC voltage leads the current: positive reactance.

• The magnetic component of an electromagnetic field, abbreviated H-Field.
• The electric field and magnetic fields are mutually perpendicular.
• Magnetic fields are measured with a loop antenna.
• Magnetic fields are blocked by special materials, such as Mu Metal.
• A magnetic field is made up of lines of force.
• Magnetic field strength is measured in oersteds.
• The total number of lines of magnetic force is the imagnetic flux
.
• Magnetic flux is measured in maxwells or webers.
• 1 weber = 10⁸ maxwells.
• Flux density is the flux per unit of cross-sectional area.
• The flux density is expressed in gauss.
• Gauss and oersteds are related by the magnetic permeability of the media the magnetic lines of force are passing through:
  Gauss = permiability x Oersteds
• When the magnetic permeability of the media is equal to 1, as it is for air, and the field strenght is 1 oersted, the magnetic induction is 1 gauss. See the figure Gauss and Oersteds.

Avogadro's number of molecules of a substance. The weight of a substance in grams, numerically equal to its molecular weight. A gram-molecule. In the case of an individual atom, a gram-atom.

• Ohm's Law shows the relationship between, resistance, voltage, and current.
• Resistance (R) is expressed in ohms, voltage (E) in volts, and current (I) in amperes.
• The relationships are:
  • E = IR
  • I= E/R
  • R= E/I

• The genertion of a difference in electrical potential across a crystal by deforming the crystal across its Y axis, which is referred to as the mechanical axis.
• This potential appears across the X axis of the crystal, which is referred to as the electrical axis.
• Conversely, the application of an electrical potential across the X axis causes the crystal to deform across its Y axis.
• These effects can be used to create an oscillator with a very stable reference frequency.
• Applications of crystal oscillators include providing reference timing signals for microprocessors. The piezoelectric effect is also used in microphones and telephone earpieces.

• The electric and magnetic components of an electromagnetic field, at frequencies above 30 MHz.
• The electric and magnetic fields are measured with the same antenna.

• Opposition to the flow of electric current, expressed in ohms.
• Resistance (R) in ohms = Voltage (E) in volts /Current (I) in amperes. This is one form of Ohm's Law.

• The amount of ac current that produces the same heating effect as a dc current flowing through the same resistance.
• Power (P) in watts = I²R
• The RMS current is 0.707 x the peak amplitude of the ac current.

• The amount of ac voltage that produces the same heating effect (power disspation) as a dc voltage across the same resistance.
• Power (P) in watts = E²R
• The RMS voltage is 0.707 x the peak amplitude of the ac voltage.

• Use three output (line) leads, and one neutral lead.
• Line voltage is measured across two phases in series.
• Maximum phase to phase voltage is 1.73 times the single phase voltage.
• The phase current is equal to the line current.

• Use three leads.
• Voltage is measured across each winding and is equal to the line voltage.
• No current flows in a delta connection unless an external load is connected.
• The line current in a delta connection is 1.73 times the single phase current.

• The percentage of a specifiied period a welding machine can operate continuously at its rated output.
• In the U.S., the specified period is 10 minutes. A machine that can operate continuously at its rated output for 6 minutes has a duty cycle of 60%.
• In Europe, the specified period is 5 minutes. A machine that can operate continuously at its rated output for 3 minutes has a duty cycle of 60%.