Wait a second!
More handpicked essays just for you.
More handpicked essays just for you.
Conceptual questions on semiconductor physics
Don’t take our word for it - see why 10 million students trust us with their essay needs.
Recommended: Conceptual questions on semiconductor physics
A Semiconductor Device
A semiconductor device which conducts electric current run in one direction only. This is the simplest kind of semiconductor device, it has two terminals and a single PN junction. One diode can be used as a half-wave rectifier or four as a full-wave rectifier.
electron tube, evacuated glass or metal envelope containing two electrodes, a cathode and an anode. It is used as a rectifier and as a detector in electronic circuits such as radio and television receivers. When a positive voltage is applied to the anode (or plate), electrons emitted from the heated cathode flow to the plate and return to the cathode through an external load. If a negative voltage is applied to the plate, electrons cannot escape from the cathode and no plate current flows. Thus a diode permits electrons to flow from the cathode to the plate, but not from plate to cathode. If an alternating voltage is applied to the plate, current flows only during the time when the plate is positive. The alternating voltage is said to be rectified, or converted to dc (direct current).
In the indirectly heated cathode type of tube shown in the illustration, the electron emitter consists of a metallic cylinder, usually nickel, coated with an electron emitter, such as a mixture of barium and strontium oxides. The heat is provided by a coil of wire (heater) located inside the sleeve but insulated from it. In the directly heated cathode (right), the heater wire itself serves as the source of electrons and is referred to as the filament.
Solid-state rectifiers, which have largely replaced the vacuum type, are also frequently referred to as diodes.
Here's a simple guide to understanding diode characteristics and their use in circuit design.
Although diodes have been around for many years, few hobbyists truly understand how the devices operate, nor are they aware of the many applications to which these little "globs of grease" are suited and so they are ill equipped to take full advantage of their various "talents." So what we'll attempt to do in this space is set you on the road to enlightenment. We won't get into the composition of the device, but instead concentrate on biasing characteristics as they relate to circuit design. But, before we begin any discussion of diode circuit design, we must first discuss current flow. That's because semiconductor diodes are much easier to control with a bias current, than with a bias voltage.
A battery is a device which converts chemical energy into electrical energy. A battery usually consists of two or more cells connected in series or parallel, you can also have a single cell battery. All cells consist of a positive electrode, and a negative electrode. An electrolyte is a liquid substance capable of conducting electricity. In this substance one of the electrodes will react producing electrons, while the other will except electrons. When the electrodes are connected to a device to be powered, called a load, an electrical current flows.
Answer: The term thermiionic emission comes from the phenomena of quantumm mechanical tunneling which takes place in some special circumstances. It sometimes happens that electrons with energy less than the barrier height to cross the barrier passing through it instead of over is called tunnneling effect. In semi conductors we can see this in heavily doped material where the current in the forward direction arises due to tunneling of the charged particles with energies close to the Fermi level but not the actual barrier height. This kind of emission due to tunneling is called field emission. Now if we increase the forward bias voltage, the electrons acquire enough energy to tunnel through the thin depletion region. To avoid this kind of tunneling and get a pure current flow we raise the temperature to a certain point such that the electrons get enough energy to cross the barrier and no longer tunnel through it. This temperature generated effect is called pure thermionic emission.
He kept the gasses in glass tubes and at the end of each side of the tube, laid an electrode. The electrodes were connected to electricity, and on one side the electrode was charged positively, and on the other side it had a negative charge. He found that it formed a glowing beam, which he called a cathode ray. He knew from previous knowledge that opposite charges attract and like charges repel, so he hypothesized that a cathode ray is a flood of small negatively charged particles moving at a high speed, because the rays flowed in the direction of the positive electrode, which meant that the rays must be negative. To test his findings, he used an experiment where he measured the ratio of charge of an electron to its mass and he discovered that the ratio is constant, and that this ratio did not depend on the kind of gas nor the type of metal used for the electrodes. Then shortly after, U.S physicist Robert A. Millikan conducted an experiment where he had to find the amount of charge carried by an electron. He used the value he found and the charge-to-mass ratio of an electron that Thomson had discovered, to determine the mass of an electron. He was extremely close to the fact that is accepted today, which is that the electron carries one unit of negative charge, and its mass is 1/1840 the mass of a
idea was that electrical current flow was similar to that of heat flow, and by
1. Strategy in the second half of the 1980s: Having innovative, high-quality products and being a reliable, responsive supplier.
'With the discovery of the first Leyden jar, it was referred to as a condenser because electricity was thought of as a fluid which could condense. The Lehden jar is a glass partially filled with water that has a wire inserted through the top of an insulating stopper (cork). When the wire is charged by static electricity, it holds the charge until the wire comes into contact with a conductor which will discharge the glass.
Diodes are basic semiconductor devices that will only allow current to flow through them in one direction only, Forward bias. Diodes are made from two differently doped layers of semiconductor material that form a PN junction. When the diode is reverse biased, the positive holes are attracted towards the negative voltage and away from the junction. Likewise the negative electrons are attracted away from the junction towards the positive voltage applied to the cathode. As higher voltages are applied in reverse polarity to the diode, the depletion layer becomes wider as the applied voltage is attracting more charge carriers away from it. The diode will not conduct with a reverse voltage when a reverse bias applied. Once the voltage is applied in the forward direction, current will flow; in this case as the voltage is increased more current flows.
There are many types of fuel cells, but they all consist of an anode, a cathode, and an electrolyte that allows positively charged hydrogen ions (or protons) to move between
When we place two objects with different temperatures in contact with each other, the heat from the hotter object will immediately and automatically flow to the colder object. This is known as conduction. Some objects make excellent conductors of heat while others make poor conductors of heat or excellent insulators. Silver, copper, and gold make excellent conductors of heat. Foams and plastics make good insulators of heat but make poor conductors. Last night for dinner, I made myself a grilled cheese sandwich and a bowl of tomato soup. I heated the soup faster than I cooked the sandwich so I poured the hot soup into a bowl and finished cooking the sandwich. Once I was done cooking, I gabbed the soup bowl and burned my hand. The heat from the soup made the bowl hot. This is an example of conduction.
In the process of producing electricity, the anode in a battery produces electrons through an oxidation reaction while the cathode accepts these electrons creating electron flow [4]. Electrons are being carried and transferred by the electrolytes – that acts like a piece of metal between the anode and the cathode [4].
A tesla coil is a high frequency and an air core transformer. The coil was created by Serbian American Physicists Nikola Tesla in 1891. The tesla coil is used to produce high voltage, low current,and high frequency alternating electricity. Tesla coils are a source of Artificial Plasmas. Tesla coils are commonly seen in many modern day entertainment such as television, as well as in plasma globes. Within a plasma globe, is an electrode, that uses the inert gasses that make up plasma. The wires within the globe transfer energy, giving the purple fluorescent light effect.
This electric field pushes the charge carriers downwards. If the material is a conductor, the electric field pushes the free electrons downwards (negative y direction). As a result, a large number of charge carriers (free electrons) are accumulated at the bottom surface of the
In thermodynamics Refrigeration is the major application area, in which the heat is transferred from a lower temperature region to a higher temperature region. The devices which produce refrigeration are known as Refrigerators and the cycle on which it operates are called refrigeration cycles. Vapour compression refrigeration cycle is the most regularly used refrigeration cycle in which the refrigerant is alternately vaporized and condensed and in the vapor phase it is compressed. Gas refrigeration cycle is the well-known refrigeration cycle in which cycle refrigerant remains in the gaseous phase throughout the cycle. Cascade refrigeration are the other refrigeration cycles discussed in this chapter; absorption refrigeration is the one more refrigeration cycle which is used where the refrigerant is dissolved in liquid before it is compressed. One more refrigeration in which refrigeration is produced by passing the electric current through two dissimilar materials is called as the thermoelectric refrigeration.
From a discovery made by one of his associates, he patented the Edison effect (now called thermionic diode), which is the basis for all electron tubes. Edison will forever be remembered for his contributions to the incandescent light bulb. Even though he didn't dream up the first light bulb ever crafted, and technology continues to change every day, Edison's work with light bulbs was a spark of brilliance on the timeline of invention.
In general, rechargeable batteries are made of multiple cells that each consist of an anode, cathode...