Basics of Electricity
Electric current is simply the flow of electrical charge - think of it like water flowing through a pipe. The faster the charge flows, the higher the current. You calculate it using I = ΔQ/Δt, where current (I) equals the change in charge (ΔQ) divided by the change in time (Δt).
Potential difference (or voltage) measures how much energy each unit of charge carries as it moves between two points in a circuit. It's like the pressure pushing water through pipes. The formula is V = W/Q, where voltage equals energy transferred divided by charge.
Resistance shows how difficult it is for current to flow through a component - imagine trying to squeeze through a crowded corridor versus an empty one. You can calculate resistance using R = V/I (voltage divided by current).
Resistivity takes this concept further by comparing different materials directly, regardless of their size or shape. The formula ρ = RA/L accounts for the material's cross-sectional area and length, giving you a true measure of how well the material conducts electricity.
Key Insight: When metals heat up, their atoms vibrate more, causing electrons to collide more frequently and increasing resistance - that's why electrical equipment can get less efficient when it overheats.
