Magnetism
Electric currents and magnetic fields are closely related. Whenever an electric current flows a magnetic field accompanies the current. When a wire is coiled up, the resulting magnetic flux becomes more concentrated. More ...
Magnetism
Magnetism is the force exerted by magnets when they attract metals or attract and repel each other. More ...
Batteries
Early in the history of electrical science, laboratory physicists found that when metals came into contact with certain chemical solutions, voltages appeared between the pieces of metal. These were the first electrochemical cells. More ...
Light Emitting Diode (LED)
An LED is a diode that converts electrical current directly into light and therefore it is more efficient than other sources of light which convert some energy into heat. When electrons recombine with holes in the depletion region they release energy in the form of light photons. More ...
Alternating Current
With DC (Direct Current), electric current flows in only one direction. With AC (Alternating Current), current direction reverses periodically. More ...
Inductive Reactance
The opposition that the coil offers to ac is called inductive reactance. Like resistance, reactance is measured in ohms. Unlike resistance, reactance changes with frequency. And in an Inductor, the Voltage leads the Current by 90 degrees. More ...
Lead-Acid Battery Chemistry
As a lead-acid battery is repeatedly recharged, sulfation will build-up on the plates and the battery will begin to loose its capacity to restore to a full charge and eventually must be replaced. More ...
Inductors in DC Circuits
When voltage first applied current through an inductive circuit is low because a magnetic field starts building in the coil, and this magnetic field creates a back electromotive force (EMF) that oppose the current in the inductor. More ...
The Diode
A diode is a semiconductor component designed to allow current to pass in one direction. To form a diode, a P type semiconductor is joined with an N type of the same semiconductor element, forming a P-N junction. Diodes are used for turning AC to DC, isolating signals, and mixing signals. More ...
Junction Field Effect Transistor (JFET)
A Junction Field Effect Transistor (JFET) consists of a channel and a pn junction. The gate controls the conductance of the channel. A JFET is a voltage controlled device, therefore no current flows into the gate. More ...
How to Read a Capacitor's Values
Due to the limited space available for printing, physically small capacitors are especially difficult to read. Therefore capacitors use a wide variety of codes to describe their characteristics. More ...
Lithium Ion Battery Chemistry
Lithium-ion (Li-ion) batteries are one of the most common portable power sources used today. Impurities in the materials used to construct a lithium battery can cause it to overheat. More ...
Electric Fields and Static Electricity
Static electricity is a phenomenon caused by a buildup of unbalanced electric charge that is not moving. We are all familiar with the static electric charge caused by dragging our feet across a carpet and then the sudden static discharge caused by grabbing a door knob. More ...
Silicon Controlled Rectifier (SCR)
A Silicon Controlled Rectifier (SCR) is a 4-layer diode that is controlled by a gate signal. It ca be turned on by a pulse on the gate. More ...
