Electrical Review for the Math and Science Professionals is geared for the math and science professionals who want to learn or even earn a Masters in electrical engineering. This website will bring the fundamentals of electrical engineering at higher level.

The Basics

Electric Current is the movement of electric charge. Electric current movement occurs between a voltage potential, or voltage difference between two points along a conductive path. Voltage potential could be a fixed source, or be alternating. A car battery is a fixed voltage, with electron flow going in one direction. This is known as Direct Current (DC). Alternating current is where the voltage potential changes polarity. A power generator, or power plant that deliver power to your house is in the form of Alternating Current (AC). Household outlets is a source of alternating current, at a fixed frequency of 60 hertz. 60 hertz means that the polarity changes across the outlet contacts 60 times a second.

When we speak of voltage potential, it is the potential to do electrical work. An analogy of this can be a water tank at a distance from the ground, with a water hose running from the bottom of the tank to a nozzle at ground level. The water tank is like a battery, higher the tank, the higher the potential. We can think of voltage potential in this case as water pressure. The nozzle is opened to cause water to spray, and now we have water flow. This water flow can be seen as 'water current'.

Let's take the circuit below. A battery is connected to a lamp. The electrons flow from the one side of the battery, through the lamp, and back to the other side of the battery. The current flows through the lamp, causing the wire element to heat and glow, it is now doing 'work'. The lamp connected across the battery forms a closed loop, allowing electrical current to flow from one side of the battery to the other.



The voltage is in units of 'Volts'. Electron flow, or current, is in units of Amperes. Most of the time we are dealing with electrical units less than a volt or amp. One millivolt is 1/1000 volts. A microvolt is 1/1000000 of a volt. Same is used with current, except it will be milliamp and microamp.

Units
m milli 1/1000
u micro 1/1000000
n nano 1/1000000000
p pico 1/1000000000000


The conventions used here in regards to current flow is that current flows from the source positive polarity point to the negative polarity.

In depth links

Electric Current
Voltage