Charge and Current

Objective: Describe charge conservation and charging mechanisms.

Electric charge is a property of matter measured in coulombs. Protons carry positive charge and electrons negative charge of equal magnitude; most everyday charging involves transfer or redistribution of electrons rather than making new charge. Like charges repel and unlike charges attract. An object can be charged by contact, rubbing, or induction with suitable grounding, while total charge in an isolated system is conserved. A neutral object has zero net charge, not no charged particles. The simplified electron-transfer model does not cover every material detail, and a measured charge depends on the system boundary.

Objective: Apply charge and current to calculations, evidence, and specified situations.

Current is charge flow per time, I=Q/Δt. Potential difference is energy transferred per charge, ΔV=ΔE/Q. Conventional current follows the direction positive charge would move; electron drift in a metal is opposite. Charge is conserved and can redistribute rather than appear from nowhere. A steady circuit requires an appropriate path and energy source. Current, charge, and voltage are different quantities with units ampere, coulomb, and volt respectively.