T5 — Electrical Principles
4 exam questions · 4 groups · 51 questions in pool
The math and vocabulary of electricity: what current, voltage, resistance, and power are and their units; converting between metric prefixes and decibels; the meaning of capacitance, inductance, and impedance; and the two formulas you must be able to use — Ohm’s Law and the power law. This subelement rewards understanding a few relationships over memorizing dozens of answers, because the questions are the same handful of ideas with the numbers swapped.
T5A — Current and Voltage; Conductors and Insulators; AC and DC
12 questions
What this group tests: the four core quantities and their units, the difference between conductors and insulators, and AC vs. DC.
Foundational concepts
Four quantities, four units — learn the pairing and a third of this subelement falls into place:
- Current is the flow of electrons, measured in amperes (A).
- Voltage is the force that pushes electrons (electromotive force), measured in volts.
- Resistance is opposition to flow, measured in ohms (Ω).
- Power is the rate energy is used, measured in watts (W).
Frequency — the number of complete cycles per second — is measured in hertz (Hz).
Conductors vs. insulators comes down to free electrons. Metals conduct well because they have many free electrons; materials like glass lock their electrons in place and make good insulators.
AC vs. DC: alternating current periodically reverses direction (positive, then negative), while direct current flows one way. Resistance opposes all current flow (AC or DC) — “all of these.”
Key facts to retain
- Current = amperes (electron flow); Voltage = volts (the force); Resistance = ohms; Power = watts (rate of energy use); Frequency = hertz (cycles/second).
- Metals conduct = many free electrons; glass insulates.
- AC reverses direction; resistance opposes any current.
External reference anchors
- NCVEC syllabus: T5A — Current and voltage: terminology and units; conductors and insulators; AC and DC
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T5A01 | Unit of current | Amperes |
| T5A02 | Unit of power | Watts |
| T5A03 | Name for electron flow | Current |
| T5A04 | Unit of resistance | Ohms |
| T5A05 | Force causing electron flow | Voltage |
| T5A06 | Unit of frequency | Hertz |
| T5A07 | Why metals conduct | Many free electrons |
| T5A08 | A good insulator | Glass |
| T5A09 | What AC is | Reverses positive/negative |
| T5A10 | Rate energy is used | Power |
| T5A11 | What resistance opposes | All these choices |
| T5A12 | Cycles per second | Frequency |
T5B — Math for Electronics: Unit Conversion and Decibels
13 questions
What this group tests: moving between metric prefixes (milli, kilo, micro, pico, mega, giga) and the decibel scale for power ratios.
Foundational concepts
Metric prefixes are just powers of ten. Learn these multipliers and every conversion question is mechanical:
- milli (m) = ×0.001 → so 1.5 A = 1500 mA, 3000 mA = 3 A, 500 mW = 0.5 W
- kilo (k) = ×1000 → 1 kV = 1000 V, 1,500,000 Hz = 1500 kHz, 3.525 MHz = 3525 kHz
- micro (µ) = ×0.000001 → 1 µV = one-millionth of a volt
- pico (p) = ×10⁻¹² → 1,000,000 pF = 1 µF
- mega (M) = ×1,000,000 → 28400 kHz = 28.400 MHz
- giga (G) = ×1,000,000,000 → 2425 MHz = 2.425 GHz
The trick is just counting decimal places: each step up the ladder (e.g., Hz→kHz→MHz→GHz) moves the decimal three places.
Decibels (dB) express ratios of power, and only three values appear on this exam:
- doubling power (×2) ≈ +3 dB; halving ≈ −3 dB. So 5 W→10 W = +3 dB.
- ×10 power = +10 dB; ÷10 = −10 dB. So 20 W→200 W = +10 dB.
- combine them: 12 W→3 W is ÷4 = two halvings = −6 dB.
Memorize “3 dB = double, 10 dB = ten times,” and you can build the rest by adding.
Key facts to retain
- Prefix ladder in steps of ×1000: pico, (nano), micro, milli, unit, kilo, mega, giga.
- 1500 mA = 1.5 A; 1 kV = 1000 V; 1,000,000 pF = 1 µF; 28400 kHz = 28.4 MHz.
- +3 dB = ×2 power, +10 dB = ×10 power (negatives = the inverse).
External reference anchors
- NCVEC syllabus: T5B — Math for electronics: conversion of electrical units; decibels
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T5B01 | 1.5 A in mA | 1500 mA |
| T5B02 | 1,500,000 Hz | 1500 kHz |
| T5B03 | One kilovolt | 1000 volts |
| T5B04 | One microvolt | One-millionth of a volt |
| T5B05 | 500 mW | 0.5 W |
| T5B06 | 3000 mA | 3 A |
| T5B07 | 3.525 MHz | 3525 kHz |
| T5B08 | 1,000,000 pF | 1 µF |
| T5B09 | 5 W → 10 W | +3 dB |
| T5B10 | 12 W → 3 W | −6 dB |
| T5B11 | 20 W → 200 W | +10 dB |
| T5B12 | 28400 kHz | 28.400 MHz |
| T5B13 | 2425 MHz | 2.425 GHz |
T5C — Capacitance, Inductance, Impedance; RF; Calculating Power
13 questions
What this group tests: three more quantities and their units, the meaning of “RF” and its abbreviations, and the DC power formula.
Foundational concepts
Two ways to store energy, two new units. Capacitance is the ability to store energy in an electric field, measured in farads (F). Inductance is the ability to store energy in a magnetic field, measured in henrys (H). Impedance is the total opposition to AC current flow, and like resistance it’s measured in ohms (Ω).
RF stands for radio frequency — signals of all types at radio frequencies. The abbreviations to recognize: kHz = kilohertz, MHz = megahertz.
Power in a DC circuit follows P = I × E (power = current × voltage). Three of the questions are just this with numbers: 13.8 V × 10 A = 138 W; 12 V × 2.5 A = 30 W; and rearranged, 120 W ÷ 12 V = 10 A. (This pairs naturally with Ohm’s Law in T5D — if you know any two of voltage, current, resistance, and power, you can find the rest.)
Key facts to retain
- Capacitance → farad (electric field); Inductance → henry (magnetic field); Impedance → ohm (opposition to AC).
- RF = radio frequency; kHz, MHz abbreviations.
- P = I × E; rearrange to I = P / E.
External reference anchors
- NCVEC syllabus: T5C — Capacitance and inductance; RF definition and units; Impedance; Calculating power
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T5C01 | Store energy in electric field | Capacitance |
| T5C02 | Unit of capacitance | The farad |
| T5C03 | Store energy in magnetic field | Inductance |
| T5C04 | Unit of inductance | The henry |
| T5C05 | Unit of impedance | The ohm |
| T5C06 | Meaning of “RF” | Radio frequency signals |
| T5C07 | Abbreviation for megahertz | MHz |
| T5C08 | DC power formula | P = I × E |
| T5C09 | 13.8 V × 10 A | 138 watts |
| T5C10 | 12 V × 2.5 A | 30 watts |
| T5C11 | Current for 120 W at 12 V | 10 amperes |
| T5C12 | What impedance is | Opposition to AC current flow |
| T5C13 | Abbreviation for kilohertz | kHz |
T5D — Ohm’s Law; Series and Parallel Circuits
14 questions
What this group tests: the single algebraic relationship between voltage, current, and resistance, and the two rules about how current and voltage behave in series vs. parallel circuits. Every calculation question is the same equation rearranged with different numbers.
Foundational concepts
There is really only one equation here, written three ways. Ohm’s Law states that voltage equals current times resistance:
- E = I × R — solve for voltage
- I = E / R — solve for current
- R = E / I — solve for resistance
The symbols matter because the pool uses letters, not words: E is voltage (it stands for electromotive force), in volts; I is current (for intensity), in amperes; R is resistance, in ohms. If you internalize “voltage is current times resistance,” you can re-derive the other two forms by dividing both sides by whichever quantity you’re not solving for. That answers T5D01–03 outright and defeats every distractor in the calculation questions, because the wrong choices are always just the wrong operation (they substitute +, −, or ÷ where × belongs, or flip the division).
For the numeric questions the method never changes: identify the two quantities given, pick the form that isolates the unknown, plug in. “3 A from 90 V” → R = 90 / 3 = 30 Ω (T5D04). “120 V across 80 Ω” → I = 120 / 80 = 1.5 A (T5D07). “0.5 A through 2 Ω” → E = 0.5 × 2 = 1 V (T5D10).
Series vs. parallel is two facts about where charge can flow. In a series circuit there is one path, so the same current flows through every component (T5D13). In a parallel circuit every component sits across the same two nodes, so each sees the same voltage (T5D14).
Key facts to retain
- E = I × R, with rearrangements I = E / R and R = E / I.
- E = volts, I = amperes, R = ohms.
- Series → current the same everywhere; Parallel → voltage the same everywhere.
External reference anchors
- NCVEC syllabus: T5D — Ohm’s Law; Series and parallel circuits
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T5D01 | Current formula | I = E / R |
| T5D02 | Voltage formula | E = I × R |
| T5D03 | Resistance formula | R = E / I |
| T5D04 | 90 V, 3 A → R | 30 ohms |
| T5D05 | 12 V, 1.5 A → R | 8 ohms |
| T5D06 | 12 V, 4 A → R | 3 ohms |
| T5D07 | 120 V, 80 Ω → I | 1.5 amperes |
| T5D08 | 200 V, 100 Ω → I | 2 amperes |
| T5D09 | 240 V, 24 Ω → I | 10 amperes |
| T5D10 | 0.5 A, 2 Ω → E | 1 volt |
| T5D11 | 1 A, 10 Ω → E | 10 volts |
| T5D12 | 2 A, 10 Ω → E | 20 volts |
| T5D13 | Same current through all | Series |
| T5D14 | Same voltage across all | Parallel |