Cheat sheet
EASA Part-66 Module 3 Cheat Sheet
Electron Theory & Static Electricity
- Not published of exam
- Atomic Structure Coulomb's Law EMF vs PD Generation Methods Conductors vs Insulators
DC Sources of Electricity
- Not published of exam
- Primary vs Secondary Cells Lead-Acid Battery NiCd Battery Internal Resistance Series vs Parallel Cells
DC Circuits Ohm's & Kirchhoff's Laws
- Not published of exam
- Ohm's Law Current Law KCL Voltage Law KVL Series Circuits Parallel Circuits
Resistance, Resistors & Power
- Not published of exam
- Colour Code Resistivity Wheatstone Bridge Power Formulas Thermistors
Capacitance & Capacitors
- Not published of exam
- C = Q/V RC Time Constant Series vs Parallel C Stored Energy Dielectric Factors
Magnetism, Inductance & DC Machines
- Not published of exam
- Faraday's Law Lenz's Law LR Time Constant Back EMF Right-Hand Rule
AC Theory, Transformers & Machines
- Not published of exam
- RMS 0.707 Peak Reactance XL and XC Resonance Transformer Ratio Star vs Delta
Quick Facts
- Exam EASA Module 3
- Credential Part-66 B1/B2 licence
- Questions 52 (Cat B1/B2)
- Time 65 min (B1/B2)
- Pass mark 75%
- Format 3-option MCQ
- Level Level 1-2 knowledge
- Blueprint Reg (EU) 2023/989
EMF vs Potential Difference EL
EMF
- Open-circuit voltage
- Total source energy
- Drives the current
PD
- Voltage under load
- Across one component
- Less than EMF
- Source vs load voltage
Atomic & Static Basics EL
- Electron Negative charge carrier
- Proton Positive, in nucleus
- Coulomb's law F = kQ1Q2/d-squared
- Charge unit Coulomb (C)
- Current unit Ampere (A)
- EMF Open-circuit driving voltage
- Potential difference Voltage under load
- Conventional flow Positive to negative
Conductors, Insulators & Generation EL
- Conductor 1-3 valence electrons
- Insulator 5-8 valence electrons
- Semiconductor 4 valence electrons
- Thermocouple Heat to EMF
- Photovoltaic cell Light to EMF
- Piezoelectric effect Pressure to EMF
- Triboelectric effect Friction makes static charge
Cells & Batteries DC
- Primary cell Not rechargeable
- Secondary cell Rechargeable
- Lead-acid electrolyte Sulphuric acid
- NiCd electrolyte Potassium hydroxide
- Series cells EMF adds together
- Parallel cells Capacity adds together
- Terminal voltage EMF minus internal drop
- Specific gravity Checks lead-acid charge state
Series vs Parallel Circuits DC
Series
- Current common
- Resistances add
- Voltage divides
Parallel
- Voltage common
- Total below smallest
- Current divides
- Common current vs common voltage
Series vs Parallel Quick Rules DC
- Need total R in series → Add all resistances
- Need total R, 2 parallel → Product over sum
- Need total R, N equal parallel → Divide by N
- Need one branch current → Ohm's law that branch
- Need one component's drop → V = I x R there
Ohm's & Kirchhoff's Laws DC
- Ohm's law V = I x R
- Current form I = V/R
- Resistance form R = V/I
- KCL Sum of currents at node = 0
- KVL Sum EMF = sum drops
- Series rule Current common, voltage divides
- Parallel rule Voltage common, current divides
- Voltage divider V2 = V x R2/Rtotal
Resistor Colour Sequence RE
- Black Brown Red Orange Yellow Green Blue Violet Grey White
- Gold band means 5% Silver band means 10% No band means 20%
NTC vs PTC Thermistor RE
NTC
- Resistance falls with heat
- Used for sensing
PTC
- Resistance rises with heat
- Used for protection
- Falls vs rises with heat
Resistor Colour Code RE
- Black Digit 0
- Brown Digit 1
- Red Digit 2
- Orange Digit 3
- Yellow Digit 4
- Green Digit 5
- Blue Digit 6
- Violet Digit 7
- Gold band Plus-minus 5% tolerance
- Silver band Plus-minus 10% tolerance
Power Triangle RE
- Power equals VI, or I-squared R, or V-squared over R
- VI: voltage x current I-squared R: current squared x R V-squared/R: voltage squared / R
Resistance & Power Formulas RE
- Resistivity R = rho x L/A
- Temp coefficient (metal) Resistance rises with heat
- NTC thermistor Resistance falls with heat
- PTC thermistor Resistance rises with heat
- Potentiometer 3-terminal variable divider
- Wheatstone balance R1/R2 = R3/R4
- Power formula 1 P = V x I
- Power formula 2 P = I-squared x R
- Power formula 3 P = V-squared/R
- Energy W = P x t
RC Time Constant Rule CA
- Tau equals R times C; five tau is full charge
- 1 tau equals 63% 5 tau is near full Discharge mirrors the charge curve
Series vs Parallel Capacitors CA
Series C
- Product over sum
- Total value drops
Parallel C
- Values simply add
- Total value rises
- Opposite of resistor rule
RC Circuit Quick Rules CA
- Need series C total → Product over sum formula
- Need parallel C total → Add all capacitances
- Need near-full charge time → Allow 5 time constants
- Need charge at 1 tau → 63% of supply
- DC steady state, no current → Capacitor acts as open
Capacitance Fundamentals CA
- Capacitance C = Q/V
- Unit Farad (F)
- Series capacitors Product over sum, like parallel R
- Parallel capacitors Values simply add
- RC time constant Tau = R x C
- Full charge About 5 time constants
- One time constant 63% charged
- Stored energy W = half C V-squared
- Higher permittivity Capacitance increases
- Wider plate gap Capacitance decreases
LR Time Constant Rule MA
- Tau equals L over R for inductive circuits
- L in henries R in ohms Same 63%, 5-tau pattern
Self vs Mutual Inductance MA
Self inductance
- One coil only
- Opposes its own change
Mutual inductance
- Two linked coils
- Induces EMF in other
- One coil vs two coils
Magnetism & Inductance Selector MA
- Need field direction → Right-hand grip rule
- Need induced current direction → Lenz's law
- Need induced EMF size → Faraday's law, rate of change
- Need LR time constant → Tau = L/R
- Need motor force direction → Fleming's left-hand rule
- Need generator EMF direction → Fleming's right-hand rule
Magnetism & Electromagnetism MA
- External flux direction North pole to south pole
- Ferromagnetic metals Iron, nickel, cobalt
- Right-hand grip rule Field around a conductor
- Reluctance Opposition to magnetic flux
- Hysteresis Flux lags magnetising force
- Remanence Retained magnetism after removal
- Flux density unit Tesla
- MMF Current x turns
Inductance & DC Machines MA
- Faraday's law EMF proportional to flux change rate
- Lenz's law Induced current opposes the change
- Inductance unit Henry
- Mutual inductance Linked coils induce EMF
- LR time constant Tau = L/R
- Coupling coefficient 1 Perfect mutual coupling
- Commutator Converts generator AC to DC
- Back EMF Opposes armature current
- Fleming's left hand Motor force direction
- Series motor High starting torque
CIVIL AC Phase Rule AC
- CIVIL: Capacitor I leads V, Inductor V leads I
- Capacitor: current leads Inductor: voltage leads 400 Hz aircraft AC
Inductor vs Capacitor Phase AC
Inductor
- Current lags voltage
- Reactance rises with frequency
Capacitor
- Current leads voltage
- Reactance falls with frequency
- CIVIL mnemonic
AC Filter & Reactance Selector AC
- Need pass low, block high → Low-pass filter
- Need pass high, block low → High-pass filter
- Need pass one band only → Band-pass filter
- Need reject one band only → Band-stop filter
- Need XL at higher frequency → Reactance increases
- Need XC at higher frequency → Reactance decreases
AC Waveform Basics AC
- RMS value 0.707 x peak
- Average value 0.637 x peak
- Form factor About 1.11
- Periodic time T = 1/f
- Aircraft AC 400 Hz standard
- Capacitive circuit Current leads voltage 90 degrees
- Inductive circuit Current lags voltage 90 degrees
- Moving-coil meter Reads average/DC only
Star vs Delta Connection AC
Star (wye)
- Line V = root3 phase V
- Line I = phase I
Delta
- Line V = phase V
- Line I = root3 phase I
- Voltage factor vs current factor
Reactance, Impedance & Resonance AC
- Inductive reactance XL = 2 pi f L
- Capacitive reactance XC = 1/(2 pi f C)
- XL with frequency Increases
- XC with frequency Decreases
- Resonance condition XL = XC
- Impedance Z = root of R-squared+X-squared
- Power factor Cos phi = R/Z
- Skin effect Current crowds toward surface
Transformers & Filters AC
- Turns ratio Vp/Vs = Np/Ns
- Ideal transformer Vp x Ip = Vs x Is
- Eddy current fix Laminated core
- Hysteresis loss fix Soft magnetic core material
- Low-pass filter Passes low frequencies
- High-pass filter Passes high frequencies
- Band-pass filter Passes one band only
- Band-stop filter Rejects one band only
Three-Phase & AC Machines AC
- Phase spacing 120 degrees apart
- Star line voltage Root3 x phase voltage
- Delta to star Divide resistance by 3
- Slip Sync speed minus rotor speed
- Synchronous speed Sets sync motor speed
- Squirrel-cage rotor No slip rings needed
- Single-phase induction motor Not self-starting alone
- Reverse 3-phase motor Swap any two leads
Common Traps
Conventional vs Electron Current Flow
- Conventional: positive to negative ≠ Electron: negative to positive
Series R vs Series C Formula
- Series R: simply add values ≠ Series C: product over sum
Capacitor vs Inductor at DC Steady State
- Capacitor: acts as open circuit ≠ Inductor: acts as short circuit
Reactance vs Frequency Direction
- XL rises as frequency rises ≠ XC falls as frequency rises
Star vs Delta Line Voltage
- Star: line V = root3 phase ≠ Delta: line V = phase V
Resistor Tolerance Colour Meaning
- Gold band means plus-minus 5% ≠ Silver band means plus-minus 10%
Self vs Mutual Inductance Scope
- Self: one coil's own field ≠ Mutual: linked separate coils
Real Exam vs Practice Bank Options
- Real EASA exam uses 3 options ≠ This practice bank uses 4
Last Minute
- 1. 52 questions in 65 minutes
- 2. 75% pass mark, no negative marking
- 3. Real exam uses three answer options
- 4. Ohm's law: V = I R
- 5. Series: current common, resistances add
- 6. Parallel: voltage common, current divides
- 7. RC time constant: tau = RC
- 8. LR time constant: tau = L/R
- 9. RMS equals 0.707 times peak value
- 10. Resonance: XL equals XC
- 11. Aircraft AC frequency is 400 Hz
- 12. Gold band tolerance equals plus-minus 5%
EASA Part-66 Module 03 — Electrical Fundamentals
- Practice Questions 123 questions Study Guide 22 topics Cheat Sheet 111 facts Flashcards 50 cards Shorts 1 short
Same family resources
- Explore More EASA Part-66 Aircraft Maintenance Licence Modules
- Continue into nearby exams from the same family. Each card keeps practice questions, study guides, flashcards, videos, and articles in one place.
EASA Part-66 Module 01 — Mathematics
- Cheat Sheet 77 facts Practice Questions 113 questions Study Guide 11 topics Flashcards 50 cards Shorts 3 short s Blogs 1 blog
EASA Part-66 Module 10 — Aviation Legislation
- Practice Questions 126 questions Study Guide 28 topics
EASA Part-66 Module 02 — Physics
- Cheat Sheet 137 facts Practice Questions 125 questions Study Guide 28 topics Flashcards 50 cards
EASA Part-66 Module 06 — Materials and Hardware
- Cheat Sheet 314 facts Practice Questions 125 questions Study Guide 40 topics Flashcards 50 cards
EASA Part-66 Module 04 — Electronic Fundamentals
- Practice Questions 125 questions Study Guide 24 topics
EASA Part-66 Module 07 — Maintenance Practices
- Practice Questions 125 questions Study Guide 51 topics Shorts 1 short
More From This Family
- Videos and articles for deeper review.
- Article EASA Part-66 Module 1 Mathematics in 2026: Current Syllabus, Question Map, and Study Plan 13 min read