🔌 Electrical Engineering I: Circuits

What you’ll learn

1. Charge in MotionDefine electric charge and current, and explain why current requires a closed circuit.Electricity is charge in motion: current, measured in amperes (one coulomb per second, after Ampère), flows only around closed loops. Lightning shows the physics at nature's scale; a lemon-battery loop shows it on a desktop.
2. Voltage: The PushDefine voltage as potential difference and connect it to Volta's battery and everyday voltage scales.Voltage is the electrical push between two points, born as a usable steady source with Volta's 1800 pile of stacked cells. Series cells add voltage — the trick inside every 9 V battery — and knowing everyday levels from 1.5 V to grid kilovolts calibrates respect.
3. ResistanceDefine resistance, read resistor values, and explain Joule heating.Resistance impedes current; Ohm established its law in 1827 against fierce skepticism. Manufactured resistors set currents and divide voltages, and resistance converts electrical energy to heat and light — the working principle of filaments, toasters, and the fire risk in undersized wires.
4. Ohm's LawApply V = IR fluently and connect it to measurement practice.Ohm's law links voltage, current, and resistance: fix two and the third follows. Multimeters embody the law — measuring volts across, amps through, ohms by injecting a known current — and potentiometers put adjustable resistance under every knob.
5. Power and EnergyCompute electrical power with P = VI and distinguish power from billed energy.Power (watts) is volts times amps, dissipating as heat at Joule's rate; appliance ratings therefore reveal current draw. Utilities bill energy — kilowatt-hours, 3.6 MJ each — integrated by meters from spinning discs to silicon.
6. Reading and Building CircuitsRead basic schematic symbols and know the prototyping path from breadboard to soldered board.Schematics encode electrical logic independent of layout. Prototypes go together on solderless breadboards — named for the literal wooden boards of 1920s radio hobbyists — and graduate to soldered, permanent construction.
7. Series CircuitsAnalyze series circuits: common current, additive resistance, proportional voltage division.Series components share one path and one current; resistances add and voltage divides in proportion — the basis of voltage dividers everywhere. One open component stops the whole chain, as old Christmas-light strings demonstrated annually.
8. Parallel CircuitsAnalyze parallel circuits: common voltage, current sharing, reciprocal resistance.Parallel branches see full source voltage and draw independent currents; total resistance shrinks as 1/R sums. Homes wire everything in parallel so devices operate independently — the panel's branch circuits each feed a parallel family.
9. Kirchhoff's LawsState and apply Kirchhoff's current and voltage laws.KCL (currents at a node balance) is conservation of charge; KVL (loop voltages sum to zero) is conservation of energy. Written at every node and loop, they crack any network — from breadboards to the continental grid, and inside every circuit simulator.
10. Combining NetworksReduce mixed series-parallel networks to equivalents and recover individual currents and voltages.Collapse parallel and series groups step by step to one equivalent resistance, compute the total current, then expand back outward — verifying with KCL. Real boards are forests of such relationships, debugged one reduced sub-circuit at a time.
11. Real Batteries and MetersModel real sources with internal resistance and use meters without disturbing the circuit.Real batteries sag under load as terminal voltage = EMF − I·r, which is why testing needs a load and why dying flashlights fade. Voltmeters use huge resistance in parallel, ammeters near-zero resistance in series — instruments obey the same laws they measure.
12. CapacitorsDescribe capacitance, smoothing, and RC timing.Capacitors store charge (C = Q/V) and release it fast: across supplies they smooth rectified ripple into steady DC, and paired with resistors their exponential charging (τ = RC) becomes electronics' universal clock — flashes, wipers, and timers.
13. Inductors and InductionExplain electromagnetic induction and the inductor's opposition to current change.Faraday's 1831 induction — changing magnetic fields create voltage — underlies every generator and transformer. Inductors (v = L di/dt) store magnetic energy and resist current change, filtering and converting power from chip-scale spirals to room-sized coils.
14. AC, DC, and the GridContrast AC and DC and explain why transformer-friendly AC won the war of the currents.Edison's 1882 Pearl Street station proved DC distribution but couldn't travel; Tesla's polyphase AC, stepped up by transformers to slash I²R losses, won decisively when Niagara's Adams plant powered Buffalo in 1896. Generators everywhere remain Faraday's law spun by water, steam, or wind.
15. Safety and the Real WorldExplain the distinct protective roles of breakers, GFCIs, insulation, and grounding.Breakers and fuses open overloaded circuits to protect wiring from fire; GFCIs apply KCL to detect milliamp leakage and protect people; insulation and grounding prevent fault paths from forming. Together with everything before, they let you read the entire electrified world — down to an EV charging session.

Questions this course answers

Grounded in trusted sources

• Charles Alexander & Matthew Sadiku — Fundamentals of Electric Circuits (6th ed., 2016)
• Paul Horowitz & Winfield Hill — The Art of Electronics (3rd ed., 2015)
• Jill Jonnes — Empires of Light: Edison, Tesla, Westinghouse, and the Race to Electrify the World (2003)
• NIST — SI units: the ampere, volt, and ohm
• U.S. National Weather Service — lightning facts
• Original papers: Ohm, Die galvanische Kette (1827); Kirchhoff (1845); Faraday, Experimental Researches in Electricity (1831)

Every Wunder lesson is built from real, reputable sources — never invented.

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