Showing posts with label basic tutorial. Show all posts
Showing posts with label basic tutorial. Show all posts
Sunday, March 11, 2007
Static electricity
It was discovered centuries ago that certain types of materials would mysteriuosly attract one another after being rubbed together. For example, after rubbing a piece if silk against a piece of glass, the silk an glass would tend to stick together. Indeed, there was an attractive force that could be demonstrated even when the two materials we seperated. Glass and silk aren't the only materils known to behave like this. Anyone who has ever brushed up agaist a latex baloon only to find that it tries to stick to then has experienced this same phenomenon. Paraffin wax and wool cloth are another pair of materials early experimenters recognized as manifesting attractive forces after eing rubed together. This phenomenon became even more interesting when it was discovered that identical materials, after having been rubbed with their respective cloths, always repelled each other. It was also noted that when a piece of glass rubbed with silk was exposed to a piece of wax rubbed with wool, the two materials would attract to one another. Furthermore, it was found that any material demonstrating properties of attraction or repulsion after being rubbed could be classed into one of two distinct categories:attracted to glass and repelled by wax, or repelled by glass and attracted to wax. It was either one or the other, there were no materials found that would be attracted to or repelled by both glss and wax, or that ractd to one without reacting to the other.
Saturday, March 10, 2007
Inductors
Inductance is used for the storage of magnetic energy. Magnetic energy is stored as long as current keeps flowing through the inductor. In a perfect inductor, the current of a sine wave lags the voltage by 90°. Inductance measured in Henry
Coil Inductance
Inductance is related to the turns in a coil as follows:
1. The inductance is proportional to the square of the turns.
2. The inductance increases as the length of the winding is increased.
3. A shorted turn decreases the inductance, affects the frequency response, and increases the insertion loss.
4. The inductance increases as the permeability of the core material increases.
5. The inductance increases with an increase in the cross-sectional area of the core material.
6. Inductance is increased by inserting an iron core into the coil.
7. Introducing an air gap into a choke reduces the inductance.
Coil Inductance
Inductance is related to the turns in a coil as follows:
1. The inductance is proportional to the square of the turns.
2. The inductance increases as the length of the winding is increased.
3. A shorted turn decreases the inductance, affects the frequency response, and increases the insertion loss.
4. The inductance increases as the permeability of the core material increases.
5. The inductance increases with an increase in the cross-sectional area of the core material.
6. Inductance is increased by inserting an iron core into the coil.
7. Introducing an air gap into a choke reduces the inductance.
Capacitor
Capacitor is an electrical device that can store electrical energy. Capacitance is the concept of energy storage in an electric field and is restricted to the area, shape, and
spacing of the capacitor plates and the property of the material separating them. Capacitance measured in Farad. Capacitor that we usually used in micro, pico, or nano Farad.
Capacitors are used to filter, couple, tune, block dc, pass ac, bypass, shift phase, compensate, feed through, isolate, store energy, suppress noise, and start motors. They must also be small, lightweight, reliable, and withstand adverse conditions.
Breakdown voltage
Capacitor have parameter that called breakdown voltage. Break down voltage is the maximum voltage that can apply to a capacitor. When we applied voltage larger than break down voltage, capacitor will damaged and some times can be exploded.
Types of Capacitors
Ceramic Capacitors
Ceramic capacitors are used most often for bypass and coupling applications. Ceramic capacitor have capacitance range from 1.0pF to 4.7uF. Ceramic capacitors have no polarity.
Ceramic capacitors should not be used for analog circuits, because they can distort the signal.
Film Capacitors
Film capacitors consist of alternate layers of metal foil and one or more layers of a flexible plastic insulating material (dielectric) in ribbon form rolled and encapsulated.
Mica Capacitors
Mica capacitors have small capacitance values and are usually used in high-frequency circuits. They are constructed as alternate layers of metal foil and mica insulation, which are stacked and encapsulated, or are silvered mica, where a silver electrode is screened on the mica insulators.
Paper-Foil-Filled Capacitors
Paper-foil-filled capacitors are often used as motor capacitors and are rated at 60 Hz. They are made of alternate layers of aluminum and paper saturated with oil that are rolled together. The assembly is mounted in an oil filled, hermetically sealed metal case.
Electrolytic Capacitors
Electrolytic capacitors provide high capacitance in a tolerable size; however, they do have drawbacks. Low temperatures reduce performance, while high temperatures dry them out. The electrolytes themselves can leak and corrode the equipment. Repeated surges above the rated working voltage, excessive ripple currents, and high operating temperature reduce performance and shorten capacitor life. Electrolytic capacitors are manufactured by an electro chemical formation of an oxide film on a metal surface.
The metal on which the oxide film is formed serves as the anode or positive terminal of the capacitor; the oxide film is the dielectric, and the cathode or negative terminal is either a conducting liquid or a gel.
spacing of the capacitor plates and the property of the material separating them. Capacitance measured in Farad. Capacitor that we usually used in micro, pico, or nano Farad.
Capacitors are used to filter, couple, tune, block dc, pass ac, bypass, shift phase, compensate, feed through, isolate, store energy, suppress noise, and start motors. They must also be small, lightweight, reliable, and withstand adverse conditions.
Breakdown voltage
Capacitor have parameter that called breakdown voltage. Break down voltage is the maximum voltage that can apply to a capacitor. When we applied voltage larger than break down voltage, capacitor will damaged and some times can be exploded.
Types of Capacitors
Ceramic Capacitors
Ceramic capacitors are used most often for bypass and coupling applications. Ceramic capacitor have capacitance range from 1.0pF to 4.7uF. Ceramic capacitors have no polarity.
Ceramic capacitors should not be used for analog circuits, because they can distort the signal.
Film Capacitors
Film capacitors consist of alternate layers of metal foil and one or more layers of a flexible plastic insulating material (dielectric) in ribbon form rolled and encapsulated.
Mica Capacitors
Mica capacitors have small capacitance values and are usually used in high-frequency circuits. They are constructed as alternate layers of metal foil and mica insulation, which are stacked and encapsulated, or are silvered mica, where a silver electrode is screened on the mica insulators.
Paper-Foil-Filled Capacitors
Paper-foil-filled capacitors are often used as motor capacitors and are rated at 60 Hz. They are made of alternate layers of aluminum and paper saturated with oil that are rolled together. The assembly is mounted in an oil filled, hermetically sealed metal case.
Electrolytic Capacitors
Electrolytic capacitors provide high capacitance in a tolerable size; however, they do have drawbacks. Low temperatures reduce performance, while high temperatures dry them out. The electrolytes themselves can leak and corrode the equipment. Repeated surges above the rated working voltage, excessive ripple currents, and high operating temperature reduce performance and shorten capacitor life. Electrolytic capacitors are manufactured by an electro chemical formation of an oxide film on a metal surface.
The metal on which the oxide film is formed serves as the anode or positive terminal of the capacitor; the oxide film is the dielectric, and the cathode or negative terminal is either a conducting liquid or a gel.
Resistor
Resistor is an electronic device that have function to reduce the electric current. The magnitude to the opposition to flow current is called resistance in the resistor. Resistance is measured in ohm. An ohm is the resistance that arises when a current of one ampere is passed through a resistor subjected to one volt across its terminals.
There are three type of resistor, fixed and variable, and special purpose resistor. Resistor also classified according to the material which they are made for. Usually resistor is made of carbon film or metal film. There are other thing that need to consider when selecting a resistor, resistor tolerance and power rating. Resistor tolerance specified in % and maximum power rating of resistor is specified in watt.
Fixed resistor
Composition Resistors
Composition resistors are composed of carbon particles mixed with a binder. This mixture is molded into a cylindrical shape and hardened by baking. Leads are attached axially to each end, and the assembly is encapsulated in a protective encapsulation coating. Color bands on the outer surface indicate the resistance value and tolerance. Composition resistors are economical and exhibit low noise levels for resistances above 1 MW. Composition resistors are usually rated for temperatures in the neighborhood of 70°C for power ranging from 1/8 to 2 W. Composition resistors have end-to-end shunted capacitance that may be noticed at frequencies in the neighborhood of 100 kHz, especially for resistance values above 0.3 MW.
Metal film resistors
Metal film resistors are used when a higher tolerance (more accurate value) is needed. They are much more accurate in value than carbon film resistors. They have about ±0.05% tolerance. They have about ±0.05% tolerance. Resistors that are about ±1% are more than sufficient. Metal-film resistors are commonly made of nichrome, tin-oxide, or tantalum nitride, either hermetically sealed or using molded-phenolic cases. The metal film resistor is used for bridge circuits, filter circuits, and low-noise analog signal circuits.
Wire-Wound Resistors
Wire-wound resistors are made by winding wire of nickel-chromium alloy on a ceramic tube covering with a vitreous coating. The spiral winding has inductive and capacitive characteristics that make it unsuitable for operation above 50 kHz. The frequency limit can be raised by non inductive winding so that the magnetic fields produced by the two parts of the winding cancel.
Variable Resistors
Potentiometers
The potentiometer is a special form of variable resistor with three terminals. Two terminals are connected to the opposite sides of the resistive element, and the third connects to a sliding contact that can be adjusted as a voltage divider. Potentiometers are usually circular in form with the movable contact attached to a shaft that rotates. Potentiometers are manufactured as carbon composition, metallic film, and wire-wound resistors available in single-turn or multi turn units. The movable contact does not go all the way toward the end of the resistive element, and a small resistance called the hop-off resistance is present to prevent accidental burning of the resistive element.
Rheostat
The rheostat is a current-setting device in which one terminal is connected to the resistive element and the second terminal is connected to a movable contact to place a selected section of the resistive element into the circuit. Typically, rheostats are wire-wound resistors used as speed controls for motors, ovens, and heater controls and in applications where adjustments on the voltage and current levels are required, such as voltage dividers and bleeder circuits.
Special-Purpose Resistors
LDR (Light Dependent Resistor)
LDR is a device whose resistance changes in response to the amount of light falling on it. An LDR's resistance value in the presence strong light is just a few ohms, but in the absence of light the value can be many tens of mega ohms. It is important to note that they are not very linear in their response. The base material from which LDRs made is cadmium sulfide or lead sulphated.
Thermistor
Thermistors are resistors that change their resistance exponentially with changes in temperature. If the resistance decreases with increase in temperature, the resistor is called a negative temperature coefficient (NTC) resistor. If the resistance increases with temperature, the resistor is called a positive temperature coefficient (PTC) resistor.
There are three type of resistor, fixed and variable, and special purpose resistor. Resistor also classified according to the material which they are made for. Usually resistor is made of carbon film or metal film. There are other thing that need to consider when selecting a resistor, resistor tolerance and power rating. Resistor tolerance specified in % and maximum power rating of resistor is specified in watt.
Fixed resistor
Composition Resistors
Composition resistors are composed of carbon particles mixed with a binder. This mixture is molded into a cylindrical shape and hardened by baking. Leads are attached axially to each end, and the assembly is encapsulated in a protective encapsulation coating. Color bands on the outer surface indicate the resistance value and tolerance. Composition resistors are economical and exhibit low noise levels for resistances above 1 MW. Composition resistors are usually rated for temperatures in the neighborhood of 70°C for power ranging from 1/8 to 2 W. Composition resistors have end-to-end shunted capacitance that may be noticed at frequencies in the neighborhood of 100 kHz, especially for resistance values above 0.3 MW.
Metal film resistors
Metal film resistors are used when a higher tolerance (more accurate value) is needed. They are much more accurate in value than carbon film resistors. They have about ±0.05% tolerance. They have about ±0.05% tolerance. Resistors that are about ±1% are more than sufficient. Metal-film resistors are commonly made of nichrome, tin-oxide, or tantalum nitride, either hermetically sealed or using molded-phenolic cases. The metal film resistor is used for bridge circuits, filter circuits, and low-noise analog signal circuits.
Wire-Wound Resistors
Wire-wound resistors are made by winding wire of nickel-chromium alloy on a ceramic tube covering with a vitreous coating. The spiral winding has inductive and capacitive characteristics that make it unsuitable for operation above 50 kHz. The frequency limit can be raised by non inductive winding so that the magnetic fields produced by the two parts of the winding cancel.
Variable Resistors
Potentiometers
The potentiometer is a special form of variable resistor with three terminals. Two terminals are connected to the opposite sides of the resistive element, and the third connects to a sliding contact that can be adjusted as a voltage divider. Potentiometers are usually circular in form with the movable contact attached to a shaft that rotates. Potentiometers are manufactured as carbon composition, metallic film, and wire-wound resistors available in single-turn or multi turn units. The movable contact does not go all the way toward the end of the resistive element, and a small resistance called the hop-off resistance is present to prevent accidental burning of the resistive element.
Rheostat
The rheostat is a current-setting device in which one terminal is connected to the resistive element and the second terminal is connected to a movable contact to place a selected section of the resistive element into the circuit. Typically, rheostats are wire-wound resistors used as speed controls for motors, ovens, and heater controls and in applications where adjustments on the voltage and current levels are required, such as voltage dividers and bleeder circuits.
Special-Purpose Resistors
LDR (Light Dependent Resistor)
LDR is a device whose resistance changes in response to the amount of light falling on it. An LDR's resistance value in the presence strong light is just a few ohms, but in the absence of light the value can be many tens of mega ohms. It is important to note that they are not very linear in their response. The base material from which LDRs made is cadmium sulfide or lead sulphated.
Thermistor
Thermistors are resistors that change their resistance exponentially with changes in temperature. If the resistance decreases with increase in temperature, the resistor is called a negative temperature coefficient (NTC) resistor. If the resistance increases with temperature, the resistor is called a positive temperature coefficient (PTC) resistor.
Electricity
Have you ever stood outside during a bad storm an seen a sudden flash light up the sky? That wa probably lighting. Lighting is very powerful. The heat froma flash of lighting can burn the ground and even set trees or house on fire. Do you know what lighting is? It's a giant spark electricity in the air.
Have you ever noticed tiny sparks when you comb your hair, or when you take off a nylon sweater very quickly in the dark? These are sparks of electricity. They are just lighting flashes, but much smaller and safer.
Our body uses electricity all the time. Our heart produces tiny amounts of electricity to help it beat properly. Our brain is receiving and sending electrical messages to every part of our body, even when we are sleep.
All animal's bodyies produces electricity, and some even use it as a weapon. Have you ever heard of the electric eel? The electric eel lives mainly in the Amazon and Orinoco rivers of South America. This eel s a fish which makes its own electricity to help it catch food and as protection against enemies. The eel's body can make enough electricity to light up 20 light bulbs,
We don't use electric eels to light up the bulbs. Most of the electricity, or electric current, we use come from huge power stations. Can you think of some ways that we use electricity? Electricity lights up bulbs so that we can see a night. Electricity heats up oven so that we can cook food. At this time we use electricity in almost of our life aspect.
Have you ever noticed tiny sparks when you comb your hair, or when you take off a nylon sweater very quickly in the dark? These are sparks of electricity. They are just lighting flashes, but much smaller and safer.
Our body uses electricity all the time. Our heart produces tiny amounts of electricity to help it beat properly. Our brain is receiving and sending electrical messages to every part of our body, even when we are sleep.
All animal's bodyies produces electricity, and some even use it as a weapon. Have you ever heard of the electric eel? The electric eel lives mainly in the Amazon and Orinoco rivers of South America. This eel s a fish which makes its own electricity to help it catch food and as protection against enemies. The eel's body can make enough electricity to light up 20 light bulbs,
We don't use electric eels to light up the bulbs. Most of the electricity, or electric current, we use come from huge power stations. Can you think of some ways that we use electricity? Electricity lights up bulbs so that we can see a night. Electricity heats up oven so that we can cook food. At this time we use electricity in almost of our life aspect.
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