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Fundamentals of Electricity

I. The Philippine Electrical Code

Definition: The Philippine Electrical Code (RA7920) is the legal framework that governs the practice, licensure, and regulation of electrical engineers and electricians in the Philippines.
Purpose: It serves as the national standard for electrical safety, ensuring the safety of individuals, buildings, and their contents.

II. Electrical Safety Devices

Shuttered Sockets:
- Description: Sockets equipped with internal protective shutters to prevent children from inserting objects into them.
Fuse:
- Function: Acts as a protective device that melts when excessive current flows, thus breaking the circuit and stopping current flow.
Circuit Breaker:
- Function: Protects against circuit overload by breaking the circuit without being destroyed, allowing for long-term use.
Ground Fault Circuit Interrupter (GFCI):
- Purpose: Designed to detect tiny mismatches in currents, preventing electrocution.
- Placement Requirements: Mandatory installation in areas prone to water exposure such as bathrooms and kitchens.
Equipotential Earth Point/Stud:
- Definition: A device used in conjunction with plug sockets to connect all equipment to a common grounding point, ensuring a uniform low potential across all devices.
Three-pronged Plug:
- Construction: A plug featuring a round prong that serves as a ground connection, enabling the device to connect to the building's ground wire.

III. Electrical Safety Procedures

Procedures Include:
- Checking extension cords and wiring for damage.
- Inspecting power tools prior to use.
- Replacing any tools with damaged insulation.
- Avoiding alterations to electrical plugs.
- Keeping extension cords inside to prevent tripping hazards.
- Using outlet covers to prevent accidental contact with live electrical components.

IV. Physiological Effects of Electric Shock

Electrolysis:
- Effect: Electrical current results in polarized ions causing ulcerations in affected tissues.
Burns:
- Description: Damage ranging from minor to severe caused by electric currents, dependent on voltage levels.
Muscle Cramps:
- Implication: Results from uncontrollable muscle twitching due to electrical overstimulation.
Ventricular Fibrillation:
- Manifestation: A severe alteration in heart rhythm resulting from electrical current, similar to muscle cramps but specifically affecting cardiac function.

V. Definition of Terms

Electric Current:
- Definition: The amount of charge flowing through a conductor per unit time, measured in Amperes (A).
- Formula: $I = \frac{q}{t}$ where:
- $q$ = charge (Coulombs)
- $t$ = time (seconds)
Types of Electric Current:
- Direct Current (DC): Constant voltage and direction, commonly used in battery-operated devices.
- Alternating Current (AC): Voltage and current direction fluctuates periodically.
- Subtypes:
  - Conventional Current: Flows from the positive to the negative terminal.
  - Electron Current: Flows from negative to positive terminal.
Current Density:
- Definition: The amount of electric current flowing per unit area, measured in $A/m^2$ .
Drift Velocity:
- Definition: The average net velocity of charged particles, typically expressed in $m/s$ .
Resistance:
- Definition: The property inherent to a material that resists electric current, measured in Ohms (Ω), defined as $\frac{V}{A}$ .
- Conductance: Inverse of resistance, a property indicating how easily electricity flows through a material, measured in Siemens (S).
Resistivity:
- Definition: The measure of a material's intrinsic resistance, denoted in Ohm-meters (Ω·m).
Effect of Temperature on Resistivity:
- Insulators: Exhibits a negative temperature coefficient, resulting in decreased resistance with increased temperature.
- Conductors: Exhibits a positive temperature coefficient, leading to increased resistance with rising temperatures.

Resistivity Data of Common Materials

Table showing Resistivity ( ho) and Temperature Coefficient ( $ext{α}$ ):

Material	Resistivity (Ω·m)	Temperature Coefficient (per °C)
Silver (Ag)	$1.59 imes 10^{-8}$	$0.0038$
Copper (Cu)	$1.68 imes 10^{-8}$	$0.00386$
Gold (Au)	$2.2 imes 10^{-8}$	$0.0034$
Aluminum (Al)	$2.65 imes 10^{-8}$	$0.00429$
Tungsten (W)	$5.6 imes 10^{-8}$	$0.0045$
Iron (Fe)	$9.71 imes 10^{-8}$	$0.00651$
Mercury (Hg)	$9.8 imes 10^{-7}$	$0.0009$
Steel (Fe3C)	$7.2 imes 10^{-7}$	$0.003$
Constantan	$4.9 imes 10^{-7}$	$0.0033$
Manganin	$4.82 imes 10^{-7}$	$2 imes 10^{-5}$
Lead (Pb)	$2.2 imes 10^{-7}$	$0.0039$
Platinum (Pt)	$1.1 imes 10^{-7}$	$0.003927$
Nichrome	$1.5 imes 10^{-6}$	$0.0004$
Coal/Graphite	$3 imes 10^{-5}$ to $6 imes 10^{-4}$	$-5 imes 10^{-4}$
Germanium (Ge)	$1 imes 10^{-3}$ to $4.6 imes 10^{-1}$	$-0.05$
Silicon (Si)	$0.1$ to $6.4 imes 10^{2}$	$-0.07$
Human Skin	$5 imes 10^{5}$ (approx.)
Glass	$1 imes 10^{9}$ to $1 imes 10^{14}$
Rubber	$1 imes 10^{13}$ (approx.)
Sulfur (S)	$1 imes 10^{15}$
Quartz	$7.5 imes 10^{17}$

Definition of Conductivity: Inverse measure of resistivity, indicating how well a material conducts electricity.

VI. Ohm’s Law and Related Concepts

Ohm's Law: Developed by Georg Simon Ohm; states that current (I) is directly proportional to voltage (V) and inversely proportional to resistance (R).
I-V Curve:
- Definition: A graphical representation displaying the relationship between current and voltage.
- Classification:
- Ohmic Device: Follows Ohm's law with a constant resistance.
- Non-Ohmic Device: Deviates from Ohm's law or shows variable resistance.
Electrical Energy:
- Conversion: Electrical energy is denoted as $U_E$ .
Power:
- Definition: The rate at which energy is transferred, measured in Watts (W).
Electromotive Force (EMF):
- Definition: Work done by the voltage source in the circuit, remains constant and is seen as the cause of voltage.
Internal Resistance:
- Definition: The resistance inherent in a power source.
Terminal Potential Difference:
- Definition: The output voltage of a source considering its internal resistance.
Electrical Hazard:
- Definition: Conditions involving humans and electrical equipment that can lead to injuries or fatalities.
Electric Shock:
- Definition: Physiological damage resulting from the flow of electric current through the body.
Lichtenberg Figure:
- Description: A branching, tree-like pattern formed in materials as a result of electric discharge.
Electrocution:
- Definition: Death resulting from electric shock.

VII. Kirchhoff’s Rules

Current Law:
- At any junction in an electrical circuit, the total current entering the junction equals the total current exiting the junction.
- Mathematical Representation: $ext{Σ}I{in} = I{out}$ .
Voltage Law:
- The sum of the potential differences (voltage) around any closed loop in a circuit must equal zero.
- Resistance Rule:
  - When traversing the loop in the direction of current: $V = -IR$ .
  - When traversing against the current: $V = IR$ .
- EMF Rule:
  - When traversing in the direction of EMF: $ext{ε} = ext{ε}$ .
  - When traversing against the EMF: $ext{ε} = - ext{ε}$ .
RC Circuit:
- Definition: A circuit that consists of a resistor and a capacitor, commonly used for filtering signals.

VIII. FORMULAE

Electric Current:
- $I = \frac{q}{t}$
- Where:
- $q$ = charge
- $t$ = time
Current Density:
- $extbf{J} = \frac{I}{A}$
- Where:
- $I$ = current
- $A$ = cross-sectional area of the conductor
Drift Velocity:
- $u = \frac{I}{An|e^{−}|}$
- Where:
- $n$ = charge carriers per unit volume
- $|e^{−}|$ = absolute value of electron charge
Resistance:
- R = rac{
  ho l}{A}
- Where:
- $l$ = length of the conductor
- $A$ = cross-sectional area
Conductance:
- $G = \frac{1}{R}$
Resistivity:
- ho = rac{E}{J}
- Where:
- $E$ = electric field
- $J$ = current density
Effect of Heat on Resistance:
- $R = R_0[1 + ext{α}ΔT]$
Effect of Heat on Resistivity:
- ho =
  ho_0[1 + ext{α}ΔT]
- Where:
- $ext{α}$ = temperature coefficient
- $ΔT$ = temperature change

IX. Electrical Power Formulas

Electromotive Force:
- $ε = I(R + r)$
- Where:
- $I$ = current
- $R$ = load resistance
- $r$ = internal resistance
Terminal Potential Difference:
- $V_T = ε - Ir$
Power Dissipated:
- $P_r = \frac{ε^2r}{(R + r)^2}$
Total Power Output:
- $Pε = PR + P_r$

X. Resistors in Circuits

Series Circuits:
- Total resistance: $RT = R1 + R2 + … + Rn$
- Total current: $IT = I1 = I2 = … = In$
- Total voltage: $VT = V1 + V2 + … + Vn$
Parallel Circuits:
- Total resistance: $\frac{1}{RT} = \frac{1}{R1} + \frac{1}{R2} + … + \frac{1}{Rn}$
- Total current: $IT = I1 + I2 + … + In$
- Total voltage: $VT = V1 = V2 = … = Vn$

XI. References

Bauer, W., & Westfall, G. D. (2016). General physics 2 (2nd ed.). Columbus, OH: McGraw-Hill Education.
Bautista, D.C. (2013). Science impact: Integrated science (3rd ed.). Antipolo City: Academe Publishing House, Inc.
Cacanindin, D.D.A., & Sharma, M. PhD (2016). General physics 2. Quezon City, Vibal Publishing House, Inc.
Freedman, R. A., Ford, A. L., & Young, H. D. (2013). Sears and Zemansky's university physics (with modern physics) (14th ed.). Addison-Wesley.
Heller, J.L. (2015). Electrical injury. Retrieved from https://medlineplus.gov/ency/article/000053.htm
Energy Safety (2012). Electrical safety devices. Retrieved from http://www.energysafety.govt.nz/consumer/safe-living-with-e- electricity/electrical-safety-devices
Additional references included from various textbooks, technical articles, and educational websites.