Electric Circuits
An ELECTRIC CIRCUIT is a CLOSED LOOP that allows ELECTRONS to flow. Three essentials: a SOURCE (battery, wall outlet) that supplies energy, CONDUCTORS (wires) that carry the flow, and a LOAD (lightbulb, motor, computer) that uses the energy. Break the loop anywhere — the flow stops. This is how light switches work: they break and complete circuits.
Series vs parallel. SERIES circuits: components connected one after another in a single loop. If one breaks, the entire circuit fails (old Christmas lights). PARALLEL circuits: components connected on separate branches. If one fails, others keep working (modern home wiring, modern Christmas lights). Most real-world circuits combine both — series and parallel sections together.
In a SERIES circuit with three lightbulbs, one bulb burns out. What happens?
Ohm's Law. The fundamental relationship: V = I × R. VOLTAGE (V, in volts) is the "pressure" pushing electrons. CURRENT (I, in amps) is the rate of flow. RESISTANCE (R, in ohms) is how much the material opposes flow. Increase voltage → more current. Increase resistance → less current. Designed circuits balance all three for the right behavior.
Build a Circuit
Get a battery, a small lightbulb, and some wires (a basic kit costs a few dollars). Connect them in a complete loop — the bulb lights! Break the connection anywhere — it goes out.
Circuits are everywhere — every appliance, every device, every charger. Knowing the basics demystifies modern technology.
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