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Current Electricity

• Minimum requirements for current flow: voltage source and a conductor.

Best Conductor

• Graphite is the best conductor of electricity among the options.

Resistance

• Conductor resistance is a hindrance to current flow.

Resistance Increase

• Conductor resistance increases with increased length.

Specific Resistance

• Specific resistance relies on the material's nature only.

Defining Specific Resistance

• Specific resistance equals the resistance of a 1 m long conductor with a 1 m² cross-sectional area at 25°C.

Temperature and Resistance

• Increasing a conductor's temperature will increase its resistance.

James Precott Joule's Experiment

• Heat produced in a current-carrying conductor is proportional to current's square.

Joule's Mechanical Equivalent of Heat

• „J" equals 4.2 Joules/calorie.

Temperature Coefficient of a Conductor

• Defined as resistance increases per ohm per degree centigrade.

Heat Production in Conductor with Current

• Heat is produced due to inter-atomic collisions.

Undesirable Side Effects of Current Heating

• Vacuum cleaner.

Carbon Resistance and Filament Temperature

• Carbon resistance increases when its filament temperature goes down.

Ohm's Law Curve

• Ohm's law has a linear curve.

Ohm's Law Condition

• Temperature should remain constant.

Ohm's Law Application

• Ohm's law doesn't apply to semiconductors.

Limitations of Ohm’s Law

• Ohm's law isn't applicable to: electric arcs, rectifying devices, and gas discharge lamps.
• It can be applied to electrolytes.

Electric Current Presence

• Presence is known by effects produced.

Electric Current Detection

• Cannot be seen or touched.

Important Current Effects

• Heating, magnetic, and electric shock effects.

Voltage as Force

• Applied voltage function as force.

Series Circuit Current

• Series circuit current are constant.

Parallel Circuit Potential Difference

• Potential difference is always constant.

Parallel Resistance Values Ratio

• Resistance values in parallel current are equal to 4:1, current ratio becomes 1:4.

Parallel Voltage Source

• Connected voltage sources are able to supply a maximum current of 20 A maximum.

Brighter Bulb in Series

• The bulb glows brighter due to resistance that's greater than A in series connections.

Bulb and Wire

• Bulb "A" will not glow.

Resistance

• A resistance of 4 ohms is connected across 100 V supply at 4 ohms "R".

Electric Press Voltage and Power Consumption

• Reduction of voltage across an electric press by 50% reduces power to 25%.

Current Taken by Two Electric Presses

• For two electric presses connected in parallel with resistances of 100 and 300 ohms, the current ratio is 3:1.

Voltmeter

• The voltmeter will become 220 V.

Conductance Elements in Parallel

• Combined conductance is G1+G2+G3.

Series Resistance

• The least power consumption happens in resistor R4.

Heater Coil

• Supply wiring doesn't glow due to resistance of heater coil being more than supply wires.

Common Power Circuit Resistors

• Wire wound resistors.

International Ohm Measurement

• International ohm is defined in terms of the resistance of a column of mercury.

Negative Coefficient of Resistance

• Thermistor.

Fuse Material Current Carrying Capacity

• Depends on: length, material, cross-sectional area.

Resistance Between Symmetrical Corners

• The effective resistance equals 5/6R.

Natural Magnet

• Called Lodestone.

Magnet Attraction

• Nickel, cobalt, and steel.

Magnetic Lines of Force

• Always travel from north to south, externally.

Magnetic Shielding Material

• Soft iron.

Magnetism After Force Removal

• Residual.

Magnetized Iron

• It's near in one of the magnet when magnetized.

Magnetic Lines of Force

• Flux.

Force Between Two Magnetic Poles

• In inverse proportion to the square of pole distance.

Magnetic Potential Measurement

• M.M.F.

Permeance Analogy

• Conductance.

Permeability Meaning

• Conductivity of the material for magnetic lines of force.

Magnetic Flux Density Equation

• B = Φ/A.

Relative Permeability (µr) Equation

• µr = B/(µ₀ x H).

Relative Permeability Given Susceptibility

• Given by 1 + (K/µ₀).

Paramagnetic Substance Permeability

• Slightly greater than one.

Permeability Value for Free Space

• 4π x 10⁻⁷ Hm⁻¹.

Magnetization in Magnetic Material

• Appears as a result of all these: Electron orbital motion, Electron spin, Spin of nucleus.

Sum of Magnetic Moments

• Magnetization.

Non-Permanent Magnet Dipole Materials

• Diamagnetic.

Negligible Dipole

• Paramagnetic materials.

Ferromagnetic Material Temperature

• Curie temperature.

Iron Permeability

Permanent Magnet Material

• All three mentioned above.

Highest Relative Permeability Materials

• Supermalloy.

Ferrimagnetic Material Behavior

• Semiconductor.

Transformer Cores

• Ferrites.

Magnetic Material

• Soft magnetic.

Low Hysteresis Loss Materials

• Low hysteresis loss materials.

Eddy Current Loss Minimization

• Increasing resistance of 'the' magnetic medium.

Degaussing Process

• Demagnetization of a metallic part.

Reduced Hysteresis Losses

• Using grain oriented silicon.

No Self-Induced Voltage

• Occurs when a dc current flows through coil.

Self-Induced Coil Non-Influence

• Self-induced of the coil is not influenced by Voltage.

Self-Inductance Coefficient Definition

• Given as NΦ/I.

Incorrect Statement

• Coefficient of coupling for a tightly coupled coil is zero statement is incorrect.

Inductance of a Coil

• Inductance characterizes specific magnetic properties.

Collapsing Field

• Tends to oppose the decay of coil current.

Stored Energy in an Inductor

• ½ LI² Joules.

Vector Quantity

• Magnetic field density.

Conductor with Current in Magnetic Field

• Force is zero.

Induction Due to Magnetic Flux Cuts

• Induction is due to Faraday's law.

Left-Hand Rules Correlates

• Current, magnetic field, and direction of force on a conductor.

Left-Hand Rule Thumb

• Represents the direction of force on conductor.

Two Air Core Coiling Coupling Coefficient

• Depends on Mutual inductance & self inductance of two coils.

Magnetic Circuit

• Current.

Magnetic & Electric Circuits

• Flux and current flow

Applied DC Voltage and Secondary Coil

• Primary current that is constant as regards secondary coil voltage.

Inductance Effect on Constant Direct Current

• It does not affect the constant direct current.

Magnetic Flux Increase

• Increasing the MMF.

Inductance Increase

• Increasing the number of turns.

Coil Smoothing Factors

• Inductance of the coil.

Leakage Factor Measurement

• Is more than unity.

Lenz’s Law and EMF

• Always opposes the cause producing it.

Sparking Causes High Inductance

• Inductance.

Air Gap in Inductor

• Prevents core saturation.

Inductive Circuit Current Growth

• Follows Exponential Law.

Inductive Circuit Time Constant Ratio Definition

• The ratio of L/R.

Inductive Circuit Time Constant Definition

• The time it takes the current in an inductive circuit to rise to 63% of its final steady state value.

Mutual inductance

• M=N2 dΦ/di where N2-no. of returns in the second coil

Coils and Mutual Inductance

• Is maximum when "touching each other".

Proportional Value of Mutual Inductance

• √L₁L₂

Coupling Coefficient Derivation

• Can obtain from K=M/√L₁L₂.

Coupling Coefficients

• Degree of the magnetic linkage.

Magnetizing Difficulty Factor

• Low permeability.

Reduce Laminated Core

• Eddy Current loses.

Area Represents Material Properties

• The area of the hysteresis loop represents hysteresis material is proportional to J/m³/s.

Hysteresis loss in a

• B 1.6

Degaussing defined:

• Demagnetizing metallic part.

Hysteresis reduced by

• Grain oriented silicon.

No Self Induced Voltage

• When a dc current flows through the coil

Electrostatics

• Absolute permittivity of a vacuum is 8.854 x 10⁻¹² f/m.

Relative Permittivity in a Vacuum

• Equals unity.

Electric Field

• The potential is the work done to bring 1 coulomb positive charge from infinity to that point in joules.

Field Intensity Units

• Newtons/Coulomb.

• Coulomb's Law for Electric Charges: Resembles Newton’s Law of Gravitation. • Dielectric Strength: Depends on moisture content, thickness, and temperature. • Insulating Medium Voltage: An insulating medium will get punctured when voltages exceed what is applied.

Highest Value of Dielectric Glass

• Mica.

Maximum Potential Gradient in a Cable

• The conductor.

Electric Charge Region:

• Electric charge is stored in the electric field. • Hollow Spherical Conductor: Has an electric field of zero inside. • Capacitor Action: Blocks D.C. and lets A.C. pass. • Capacitor Capacity Influence: Area of the plates, dielectric and how far plates area. • Practical Capacitor Charge with 200V: 2.0 mC with a 10 Microfarad capacitor. • Dielectric Effect: Increases capacitance. • Electrolytic Capacitor Disadvantages: Low insulation resistance and only suitable for direct current. • Radio Gang Condenser Type: Air capacitor.

Maximum Sphere Potential

• 3 million volts.

Capacitor Series Time Constant

• The time constant of the circuit equals .1 seconds.

Pure Capacitor Dissipation

• Zero.

Electric Charge Storage

• Dielectric. • Parallel Condenser Capacitance: Is 16uF. • Field Strength: E= V/d. • Farad’s Measurement: The measurement of 1V per coulomb. • Electric Field Strength When Dielectrics Exist: Decreases the original value. • Parallel Dielectric Increase with Air and Mica: Increasing the area of the plates. • Parallel Plate Capacitor- Electric Side, the dielectric Slab: E/7 = the electric Side. • Parallel Plate Capacitor - Constant Capacitor with a Dielectric slab: Is at zero. • Capacitance with Dielectric
• Becomes C₀/₇. • 30uf Capacitor with 200 Vdc source.
• Is at zero. • Inductance Circuit Time.
• RC.

Change in Circuit Voltage

• A capacitance.

Electric Charge in Capacitor (Storage):

• Stored "Dielectric. • Heat of Capacitor: Is usually a leakage source. • Shorted Capacitor: Has a zero.

Electrolysis and Storage Battery

Electro-Chemical Equivalent Is

• Mass of the element liberated per unit of hydrogen. The mass is:

• Is Material Proportional to Quantity of Electricity and Electro-Chemical Equivalent.

  All substances: Equal to 96500 Coulombs.

Mass of An Ion

• Is directly a D.C. statement to laws of electrolysis • Positive Electrode (Electroplating): Called anode. • Electrolyte Impurity: Can cause an internal short-circuit, or local action. • Distilled Water Electrolyte Use (Reason): To prevent or slow action. • Liquid Electrolyte Measured by: Specific gravity. • Primary Cell Voltage Indicator: Is the type of plates and electrolytes. • Primary Cell Local Action Result: Can be rectified by amalgamating the zinc electrode with the mercury" • Dry Cell (Change): Is to change chemical action to chemical energy. • Dry Cell Polarization Resolution: Has chemical means. • Main Primary Cell Defects: Are polarization and sulphation. • Average Dry Cell Voltage: 11.3 v average ( volts )
• Dry Cell- High voltage use from : Magnesium cell _ A Dry cell is a indefinite time store, with a high internal resistance and needs no depolarizer.

Prefers (wet cell) Reason 1

• high value of EMF, which are preferred
• Lechanche cell is a intermittent work with no large currents or voltage requirements."
• Cell Voltage / Internal Resistance (Series) " I = nE / (R + nr)

Cells in Parallel

• Increase internal resistance and voltage output..
• Maximum voltage
• Supplied by an ordinary is approx 1.5 V Function Of "Zinc cell " (Carbon Based ) "Converts the hydrogen into water, from container to electrolyte as normal.

Dry Cell (Depolarizers)

"Manganese Dioxide

Secondary Cell

• The Advantage can recharge Component Composition (Secondary) ""zinc, carbon, and/or dilute sulfuric acid"",

Accumulators (types)

"lead, lead peroxide + dilute sulfuric acid is becoming more popular for power" because recharges for a longer life.

• Large output cell "power is short but CAN Recharged !"
• Gassing "During Charging /Accumulator

Secondary Cell Determined With:

"terminal voltage and strength- Lead Accumulator: The lead needs recharging of electrolyte at 1.15 as the limit. "Type Accumulator Other / Leads"

• Nickel - Cardmium
• Electrolyte Adding Method"Sulfuric Acid Adding TO Water"

low electrolyte

• is a need for distilled water! " Amp Hours. The Area A 6 ampere 60amp will provide for 6 hours". Terminal Corrosion : petroleum jelly ( used)

Discharge battery internal.

• MORE Sulfation is a " LONG TIME MAIN DISCHARGE BATTERY.

Partially lead

Adding D.C. voltage will charge as "normal" Mercury Oxide. : Is a 50% known as the " Primary Sell (Type )

Chared caused

• Electrolyte =Stronger.

• Separaters "Prevent shorting "touching of the electrolyte

• Affect capacity = discharge.

Prevent gassing

The charge rates lowered cause gassing. Cell Voltage"chemical.

• mercury-cadmium is a high voltage A.C. and D.C = Keep in well and keep it connected.

D.C MOTORS

###Electric Motors Effect:

• Magnetic as Well as Heating effect

###Rotating D.C

• Amature and Brush

Commutator

• To Change Direct from Alternating voltage

Carbon Brushes (use )

• Path for current

"VOLATAGE DC equation" V = Eb+laRa

###Maximum

• Eb = 2 / V

Speed D.C. is:

• Directly Proportional to Inversely/ Flux" or high test is speed.
• equal Infinity value is rated" or "Iron Losses( in the amature.

Dummy ( Coil)

• "MECHANICAL BALANCER" "External resistance is added"To increase the output.

Speed and Output increased

Reducing fill current

• if increases" is speeded (EMF) " Current = (AC as well as the " D.C",
• Speed reduced" is speeded (slightly )"

Current

"Drawn as " = ( V - Eb / a

Amature Torque

_T = 0.159 Ebla/N Nm ( Nm.) Armature wound

• Emf 120 = V

• Force -N.

(D.C. GENERATOR

###Commulation

• Is Getting reversed "Compensating"
• Dematerializing The DC effect." "

Equalizer

A.C. And B.C.

"Load /Winds = Variation

" inter pole = Neutral (ARMATURE)

• Inter pole " in the series"with armature EQUALIZER = BOTH "
• Generators Prefered
• • ALl the above = RUN"

Equal connection requires compound generator = when paralleling

D.C. (Generator)

A.C/ B SHUNTS

• Speed " The saturation "AMATURE ( Laminated " Edy)

Generator Variation (load "COPEER"

• Regulation "1 % REGULATION" ""

A.C Motor = "High "

D.C. DC " Shunt /Generator"

==End of Note==