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Monday, January 5, 2015

Introduction to Current

Q1: What is current?
A1: Current is the amount of positive charge that passes through a given area per unit of time.

Q2: What are the units for current?
A2: The basic unit for current is defined as the ampere (A). It is one of the seven fundamental SI units. One ampere is equal to one unit of one coulomb per second. Amperes are commonly called amps.

Q3: I took another look at the definition of current in A1. Wouldn't this mean that if electrons are flowing in a particular direction in my circuit, then the current would be flowing in the opposite direction?
A3: You are absolutely correct: positive current would be in the direction opposite to electron flow. If current were redefined as the amount of negative charge that passes through a given area per unit  time, then positive current would be in the same direction of electron flow. The fact that current is defined in reference to the flow of positive charge is a product of historical convention.

Q4: Why do should I keep track of currents over time?
A4: Changes in current usually tell us that something interesting is happening in a circuit.


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