CAPASITOR

Capasitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate.

Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters.

Capacitors are occasionally referred to as condensers. This is considered an antiquated term in English, but most other languages use an equivalent, like "condensateur" in French, "Kondensator" in German, "condensatore" in Italian, "condensador" in Spanish, or "Kondensa" in Japanese.

Contents

• 1 History
• 2 Theory of operation
  • 2.1 Capacitance
  • 2.2 Energy storage
  • 2.3 Hydraulic analogy
  • 2.4 Aging
• 3 Electric circuits
  • 3.1 DC sources
  • 3.2 AC sources
    • 3.2.1 Impedance
    • 3.2.2 Laplace equivalent (s-domain)
  • 3.3 Displacement current
  • 3.4 Networks
    • 3.4.1 Series or parallel arrangements
  • 3.5 Capacitor/inductor duality
• 4 Capacitor types
  • 4.1 Dielectric materials
  • 4.2 Structure
• 5 Applications
  • 5.1 Energy storage
  • 5.2 Power conditioning
    • 5.2.1 Power factor correction
  • 5.3 Filtering
    • 5.3.1 Signal coupling
    • 5.3.2 Decoupling
    • 5.3.3 Noise filters, motor starters, and snubbers
  • 5.4 Signal processing
    • 5.4.1 Tuned circuits
  • 5.5 Other applications
    • 5.5.1 Sensing
    • 5.5.2 Pulsed power and weapons
• 6 Hazards and safety
  • 6.1 High voltage
• 7 See also
• 8 Notes
• 9 References
• 10 External links

RESISTOR

A resisto is a two-terminal electrical or electronic component that opposes an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's law: V = IR. The electrical resistance R is equal to the voltage drop V across the resistor divided by the current I through the resistor. Resistors are used as part of electrical networks and electronic circuits.

Contents

• 1 Identifying resistors
  • 1.1 Four-band axial resistors
  • 1.2 Preferred values
  • 1.3 5-band axial resistors
  • 1.4 SMT resistors
  • 1.5 Industrial type designation
• 2 Resistor standards
  • 2.1 Power dissipation

    

  • 2.2 Series and parallel circuits
• 3 Technology
  • 3.1 Carbon composition
  • 3.2 Carbon film
  • 3.3 Thick and thin film
  • 3.4 Metal film
  • 3.5 Wirewound
  • 3.6 Foil resistor
  • 3.7 Grid resistor
  • 3.8 Strain gauges
  • 3.9 Other types
• 4 Noise
• 5 Failure modes and pitfalls
• 6 See also
• 7 References
• 8 External links

From:wikipedia , free encyclopedia

TRANSISTOR

In electronic,transistor is a semiconductor device commonly used to amplify or switch electronic signals. The transistor is the fundamental building block of computers, and all other modern electronic devices. Some transistors are packaged individually but most are found in integrated circuits.

Contents

• 1 Introduction
• 2 History
• 3 Importance
• 4 Comparison with vacuum tubes
  • 4.1 Advantages
  • 4.2 Disadvantages
• 5 Types
  • 5.1 Bipolar junction transistor
  • 5.2 Field-effect transistor
  • 5.3 Other transistor types
• 6 Semiconductor material
• 7 Packaging
• 8 Usage
  • 8.1 Switches
  • 8.2 Amplifiers
  • 8.3 Computers
• 9 See also
• 10 References
• 11 Further reading
• 12 External links
  • 12.1 Datasheets
  • 12.2 Patents
    
  From:Wikipedia ,the free encyclopedia
  

Safety

Lithium-ion batteries can rupture, ignite, or explode when exposed to high temperature environments, for example in an area that is prone to prolonged direct sunlight. Short-circuiting a Li-ion battery can cause it to ignite or explode, and as such, any attempt to open or modify a Li-ion battery's casing or circuitry is dangerous. Li-ion batteries contain safety devices that protect the cells inside from abuse, and, if damaged, can cause the battery to ignite or explode.
Contaminants inside the cells can defeat these safety devices. For example, the mid-2006 recall of approximately 10 million Sony batteries used in Dell, Sony, Apple, Lenovo/IBM, Panasonic, Toshiba, Hitachi, Fujitsu and Sharp laptops was stated to be as a consequence of internal contamination with metal particles. Under some circumstances, these can pierce the separator, causing the cell to short, rapidly converting all of the energy in the cell to heat resulting in an exothermic oxidizing reaction, increasing the temperature to a few hundred degrees Celsius in a fraction of a second.[41] This causes the neighboring cells to heat up, causing a chain thermal reaction. The mid-2006 Sony laptop battery recall was not the first of its kind, however it was the largest to date.
During the past decade there have been numerous recalls of lithium-ion batteries in cellular phones and laptops owing to overheating problems. In October 2004, Kyocera Wireless recalled approximately 1 million batteries used in cellular phones, due to counterfeit batteries produced in Kyocera's name. In December 2006, Dell recalled approximately 22,000 batteries from the U.S. market. March 2007, Lenovo recalled approximately 205,000 9-cell lithium-ion batteries due to an explosion risk. In August 2007, Nokia recalled over 46 million lithium-ion batteries, warning that some of them might overheat and possibly explode.[44] There was an incident in the Philippines involving a Nokia N91, which uses
the BL-5C battery. It is possible to replace the lithium cobalt oxide cathode material in li-ion batteries with lithiated metal phosphate cathodes that are not as sensitive to temperature, and so are less prone to explode. This also extends their shelf life. However, currently these 'safer' li-ion batteries are mainly destined for electric cars and other large-capacity battery applications, where the safety issues are more critical. Unfortunately, a problem with these 'safer' li-ion batteries is that lithiated metal phosphate batteries only about 75 percent as much energy.Another option is to use manganese oxide or ironphosphate cathode.

Storage temperature and charge

Storing a Li-ion battery at the correct temperature and charge makes all the difference in maintaining its storage capacity. The following table shows the amount of permanent capacity loss that will occur after storage at a given charge level and temperature.It is significantly beneficial to avoid storing a lithium-ion battery at full charge.A Li-ion battery stored at 40% charge will last many times longer than one stored at 100% charge, particularly at higher temperatures.

If a Li-ion battery is stored with too low a charge, there is a risk of allowing the charge to drop below the battery's low-voltage threshold, resulting in an unrecoverable dead battery. Once the charge has dropped to this level, recharging it can be dangerous. Some batteries therefore feature an internal safety circuit which will prevent charging in this state, and the battery will be for all practical purposes dead.In circumstances where a second Li-ion battery is available for a given device, it is recommended that
the unused battery be discharged to 40% and placed in the refrigerator to prolong its shelf life. While the battery can be used or charged immediately, some Li-ion batteries will provide more energy when brought to room temperature.

Battery specifications

Energy/weight ---160 Wh/kg

Energy/size ---270 Wh/1

Power/weight ---1800 W/kg

Charge/discharge efficiency--- 99.9%

Self-dicharge rate--- 5%-10%/month

Cycle durability ---1200 cycles

Nominal Cell Voltage--- 3.6 / 3.7 V

Lithium-ion battery

Lithium-ion batteries (sometimes abbreviated Li-ion batteries) are a type of rechargeable battery in which a lithium ion moves between the anode and cathode.The lithium ion moves from the anode to the cathode during discharge and from the cathode to the
anode when charging.
Lithium ion batteries are commonly used in consumer electronics. They are currently one of the
most popular types of battery for portable electronics,with one of the best energy-to-weight ratios, no memory effect, and a slow loss of charge when not in use. Certain kinds of mistreatment may cause Li-ion batteries to explode.
In addition to uses for consumer electronics, lithium-ion batteries are growing in popularity for defense, automotive, and aerospace applications due to their high energy density.
The three primary functional components of a lithium ion battery are the anode, cathode, and
electrolyte, for which a variety of materials may be used. Commercially, the most popular material for the anode is graphite, although materials such as TiS2 were originally used.[3] The cathode is generally one of three materials: a layered oxide, such as cobalt
oxide, a polyanion, such as lithium iron phosphate, or a spinel, such as manganese oxide. Depending on the choice of material for the anode, cathode, and electrolyte the voltage, capacity, life, and safety of a lithium ion battery can change dramatically.
Lithium ion batteries are not to be confused with lithium batteries, the key difference being that lithium batteries are primary batteries containing metallic lithium while lithium-ion batteries are secondary batteries containing an intercalation anode material.