What is the unit of electric current?

Electric current is measured in Amperes (A or 'amps'). One ampere = one coulomb of charge per second. Key electrical quantities and units: (1) Current (I) — flow of charge — Amperes (A); (2) Voltage (V) — electrical potential difference — Volts (V); (3) Resistance (R) — opposition to current flow — Ohms (Ω); (4) Power (P) — rate of energy transfer — Watts (W); (5) Charge (Q) — electric charge — Coulombs (C); (6) Energy — Joules (J). Ohm's Law: V = IR (voltage = current × resistance). Solve for any variable: I = V/R, R = V/I. Power: P = VI = I²R = V²/R. Series circuits: same current through all components; voltages add; total resistance = sum of resistances. Parallel circuits: same voltage across all components; currents add; 1/R_total = 1/R₁ + 1/R₂ + ... Direct Current (DC): constant direction; batteries, solar cells. Alternating Current (AC): direction reverses periodically; household electricity (60 Hz in US, 50 Hz in much of world). Conductors (low resistance): metals, especially copper, silver, gold. Insulators (high resistance): rubber, plastic, glass, dry wood. Semiconductors (intermediate): silicon, germanium — used in electronics. Electricity safety: avoid wet locations, GFCI outlets, breakers and fuses prevent overcurrent.