Electronics Information
What to know
Electronics Information covers how basic circuits and components behave. Voltage is electrical pressure, current is the flow of charge in amperes, and resistance opposes flow in ohms. Ohm's law links them: V = I × R. Power is P = V × I, which also appears as I²R or V²/R.
Series circuits have one path: current is the same everywhere, voltages add, and resistances add. Parallel circuits give each branch the full source voltage: branch currents add, and total resistance is smaller than the smallest branch.
Know the parts: resistor limits current, capacitor stores charge and blocks DC, inductor stores energy in a magnetic field, diode is a one-way valve, transistor switches or amplifies. Also review AC versus DC, conductors versus insulators, and the resistor color order: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9.
Traps
- Swapping current and voltage in a definition.
- Adding resistances in a parallel circuit, or forgetting to invert after summing reciprocals.
- Mixing milliamps and amps; 250 mA is 0.25 A.
Rule of thumb
An open path means no current at all. Check continuity before you calculate anything.
Worked example
A 12-volt source drives a 4-ohm resistor. I = V ÷ R = 12 ÷ 4 = 3 A. Power P = V × I = 12 × 3 = 36 W. Put a second 4-ohm resistor in series and total resistance is 8 ohms, so current drops to 1.5 A and total power to 18 W.