⚡ Famous Electrical Laws
1. Ohm’s Law
Formula: V = I × R
Meaning: Voltage across a conductor is directly proportional to the current through it
and its resistance.
Example: If resistance is 10 Ω and current is 2 A, then voltage = 20 V.
2. Kirchhoff’s Current Law (KCL)
Statement: The sum of all currents entering a node (junction) equals the sum of all
currents leaving that node.
Meaning: No current is lost at a connection point.
Example: If 5 A enters and 3 A leaves one path, 2 A must leave the other path.
3. Kirchhoff’s Voltage Law (KVL)
Statement: The sum of all voltages around any closed loop in a circuit is zero.
Meaning: Energy is conserved as you go around a circuit loop.
Example: Battery voltage equals the sum of voltage drops across resistors.
4. Faraday’s Law of Electromagnetic Induction
Statement: A change in magnetic field within a coil induces an electromotive force
(EMF) in the coil.
Formula: EMF = -dΦ/dt
Meaning: Moving magnets near coils produce electricity.
5. Lenz’s Law
Statement: The direction of induced EMF and current will oppose the change in
magnetic flux that caused it.
Meaning: Nature resists changes — like magnetic brakes!
6. Coulomb’s Law
Statement: The force between two electric charges is proportional to the product of their
charges and inversely proportional to the square of the distance between them.
Formula: F = k × (q₁ × q₂) / r²
Meaning: Like charges repel, unlike charges attract.
7. Gauss's Law
Statement: The total electric flux out of a closed surface is proportional to the enclosed
electric charge.
Formula: Φ = Q/ε₀
Meaning: Used to calculate electric fields of symmetrical charge distributions.
8. Ampère’s Law
Statement: The magnetic field around a closed loop is proportional to the electric current
Formula: ∮B · dl = μ₀I
passing through the loop.
Meaning: Currents create magnetic fields.
9. Joule’s Law of Heating
Statement: The heat produced in a conductor is proportional to the square of the current,
resistance, and time.
Formula: H = I²Rt
Meaning: High current heats up wires (important for ship wiring safety too!).
10. Thevenin’s Theorem
Statement: Any linear two-terminal circuit can be replaced by an equivalent circuit with
a single voltage source and series resistance.
Meaning: Simplifies complicated circuits.
🌟 Quick Fun Fact
Most practical shipboard electrical troubleshooting often uses Ohm's Law, Kirchhoff’s Laws,
and Faraday’s Law daily!
⚡ Full Details of Famous Electrical Laws
1. Ohm’s Law
Formula: V = I × R
Where:
V = Voltage (volts)
I = Current (amperes)
R = Resistance (ohms, Ω)
Principle: Electrical voltage is proportional to current and resistance.
Real-World Example: If you know a motor needs 5 A and has 2 Ω resistance, voltage =
5 × 2 = 10 V.
Application:
o Basic circuit design.
o Troubleshooting dead equipment (check voltage drop).
o Checking ship sensor circuits (RTD sensors, pressure sensors).
2. Kirchhoff’s Current Law (KCL)
Statement: The total current entering a junction = total current leaving it.
Formula: ΣI(in) = ΣI(out)
Principle: Conservation of charge — no charge disappears.
Real-World Example:
o 10 A enters a busbar, and 4 A + 6 A go out via two cables.
Application:
o Generator load-sharing systems.
o Power distribution on switchboards.
3. Kirchhoff’s Voltage Law (KVL)
Statement: Sum of all voltage drops around a closed loop = 0.
Formula: ΣV = 0
Principle: Conservation of energy — what you gain in voltage you lose across
components.
Real-World Example:
o Battery (24V) feeds lamp (18V drop) + resistor (6V drop): 18V + 6V = 24V.
Application:
o Checking battery circuits, navigation light circuits.
o Locating faults in cable loops.
4. Faraday’s Law of Electromagnetic Induction
Formula: EMF = -dΦ/dt
Where:
Φ = Magnetic flux (Webers)
dΦ/dt = Rate of change of flux
Principle: A changing magnetic field produces electricity.
Real-World Example:
o Alternators in ships work because rotors spin inside magnetic fields.
Application:
o Generator operation.
o Motor braking systems.
5. Lenz’s Law
Statement: Induced EMF creates current that opposes the change causing it.
Meaning: Nature fights changes.
Real-World Example:
o Ship's alternator field winding is arranged to produce opposition to sudden load
changes.
Application:
o Generator load control.
o Inductive braking.
6. Coulomb’s Law
Formula: F = k × (q₁ × q₂) / r²
Where:
F = Force between charges
q₁, q₂ = Amount of charges
r = Distance between them
k = Coulomb constant
Principle: Electrostatic force between two charges.
Real-World Example:
o Insulators and charged surfaces (ship antennas during storms).
Application:
o Static protection on ships.
o Radio wave studies.
7. Gauss’s Law
Formula: Φ = Q/ε₀
Where:
Φ = Electric flux
Q = Enclosed charge
ε₀ = Permittivity of free space
Principle: The electric field depends on the total enclosed charge.
Real-World Example:
o Used in complex electric field calculations for antennas.
Application:
o Radar and communication systems.
8. Ampère’s Law
Formula: ∮B · dl = μ₀I
Where:
B = Magnetic field
I = Current enclosed
μ₀ = Permeability of free space
Principle: Current creates a magnetic field.
Real-World Example:
o Coils, motors on ships.
Application:
o Designing electromagnets.
o Analyzing motor magnetic fields.
9. Joule’s Law of Heating
Formula: H = I²Rt
Where:
H = Heat (Joules)
I = Current (A)
R = Resistance (Ω)
t = Time (s)
Principle: Electrical energy converts into heat in conductors.
Real-World Example:
o Overheated cables on generator circuits due to excess current.
Application:
o Choosing correct cable size.
o Monitoring motor temperatures.
10. Thevenin’s Theorem
Statement: Any complex two-terminal circuit can be replaced with a simple equivalent
circuit (single voltage source + single resistance).
Meaning: Simplifies analysis of complicated circuits.
Real-World Example:
o Troubleshooting shipboard PLC (Programmable Logic Controller) outputs.
Application:
o Analyzing circuits quickly.
o Designing backup circuits.
🌟 Final Summary Table
Law Main Idea Shipboard Example
Ohm’s Law V=I×R Checking power in small motors
Current and Voltage
Kirchhoff’s Laws Busbar inspections
conservation
Faraday’s Law Magnetic field produces EMF Alternators and generators
Lenz’s Law Induced current opposes change Generator load reactions
Coulomb’s Law Force between charges Static protection
Gauss’s Law Electric flux related to charge Radar calculations
Ampère’s Law Current creates magnetic field Motor operation
Joule’s Law Electrical heating Cable heating issues
Simplified fault finding in control
Thevenin’s Theorem Simplify circuits
systems
⚡ Quick Conclusion
Without understanding these basic electrical laws, it’s impossible to maintain, troubleshoot, or
operate shipboard electrical systems safely and efficiently!
