Electric Charge and Current

The moving charge behind every circuit.

Matter carries positive and negative charge; like charges repel and unlike charges attract. In a metal, some electrons are free to move, and when they are pushed in one direction we get an electric current. Current is the charge passing a point each second, measured in amperes.

By convention, current is drawn in the direction positive charge would move, which is opposite to the drift of electrons. The electrons themselves drift slowly, but the push travels through the wire almost at the speed of light, so a lamp lights the moment a switch closes.

• One ampere equals one coulomb of charge per second.
• Conventional current runs opposite to electron drift.
• A complete loop is needed for steady current.

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