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Circuits
Overachieving and under-appreciated, circuits are the foundation that our technological society is built on. Now's your chance to find out not only how they work, but why. Questions regarding the physics behind voltage, resistance, capacitance, inductance, transistors, LEDs, switches, and power supplies; and how they're used to create analog and digital circuits, should be directed here.
1,646 Questions
Depending on how the transistor is biased and various other circuits connected to it, a transistor acts as an amplifier and/or switch.
When acting as an amplifier the circuit containing the transistor can do things like transmit or receive radio signals, perform analog mathematical calculations, generate waveforms, etc.
When acting as a switch the circuit containing the transistor can do things like turn on/off a light, turn on/off a motor, perform digital logic or mathematical operations, fetch and decode computer instructions, etc.
Exactly what a transistor can do is really only limited by the system requirements and the designer's imagination as to how to meet those requirements.
There are several different types of transistors: bipolar junction transistors (BJTs), field effect transistors (FETs), unijunction transistors (UJTs), programmable unijunction transistors (PUJTs), spacitors, surface barrier transistors (SBTs), tetrode transistors (TTs), point contact transistors (PCTs), etc.
What is caused by a short circuit?
A short circuit is a low resistance connection where one is unexpected. It causes a diversion of current from the intended load, and, since it is usually a higher than expected current, it often causes the protective device (fuse, circuit breaker, or relay control logic) to trip.
Which component is used to measure the current in a circuit?
an ampmeter.
Most DVM's have them, or you can use a clamp on style.
What is a material through which charges cannot move easily?
That material would be included in the category of electrical "insulators".
What is the function of an under voltage relay?
under voltage relay is used to protect the electrical equipment from the low voltage below the rated voltage till 80% of the network potential.
u/v relay is used to give a signal to emergency generator to start whenever the system voltage drops below (80%).
U/V relay number is (27) which is available in most electrical circuits to protect the following circuits by insulating them whenever the low voltage occurs:
LV/MV switch boards.
Motor feeders
Generator Circuits
Transformer circuits
u/v relay is considered to be one of the main protective relays in electrical design.
Heat sensor with fan cooling with op-amp?
heat sensor with fan cooling it will be used for cpu . it will be cool thing the mother board it will be reduce cpu temperature.........
What are the advantages and disadvantages of parallel connection of generators?
The advantage of generators in parallel is that the total electrical power output of the generators are additive.
The disadvantage of generators in parallel is the additional equipment and the extra cost of that equipment, that is needed to syncronize the generators. This extra equipment also must keep the generators in parallel and not let one generator take the lead. If this happens, that generator will take the full load and probably trip off line. This action then overloads the other paralled generator an then it to will trip off line.
What happens if there is too much current in the circuit?
It causes the disruption of the fuse, switching off the disjunctor, or set on fire the conductors if there isn'ta circuit protector and therefore burns the parts of the electric device. The cause of too much current in a ciucuit is always a resistance that has a low value. To check the cause of the excess of current in a circuit is necessary to measure all the components.
How does the Kelvin bridge differ from the wheatstone bridge?
kelvin's bridge is the modified version of wheatstone bridge and used to measure resistance values less than 1 ohm.
In the unknown of measuring the voltage what should be the setting of VOM selector?
Use the highest available voltage setting. One should know the system voltage before attempting to measure, other wise it may lead to accidents.
How many electrical plugs can you put on one circuit?
It depends on the items you will plug into the power strip. Certain appliances require much more power than others. VCR's, phone chargers, DVD/CD players don't require much power depending, whereas a toaster or microwave may take 10 to 100 times the amount of power required. Acceptable areas for power strips are within a computer setup, or a home entertainment setup. They are not recommended in the bathroom or in the kitchen at all.
What is the effect of a short circuit on other devices in the circuit?
Electricity is designed to complete a circuit. For example, it comes into your house by way of the hot wire. Then it goes through the electrical box and through the fuse system. Finally it goes through a light bulb or some other electrical devise. Then it goes back through the neutral wire. It wants to get back to the neutral wire without doing any work. In a way, electricity acts like a river. A little stream leaves the river to run your lightbulb. However, every now and then, there is a short circuit. The circuit leading to the light bulb develops a short circuit. In that case, a lot more electricity than should tries to go through the little wire that led to the light bulb. It wants to get to the neutral wire. It is like a river overflowing through a little stream and creating a flood. It can burn out the little wire and set the house on fire. The flood runs into a culvert which holds back the flood. The short circuit blows a fuse or throws a circuit breaker and the house does not burn down. Every now and then the main fuse box blows out and a house burns down. Every now and then a wire falls down outside and people walk close to it. The ground is full of electricity and the people are killed. So a short circuit happens when electricity completes a circuit without doing any work. It is dangerious when a fuse does not blow.
What is the conclusion for the wheatstone bridge experiment?
This lab effectively showed how the Wheatstone bridge provides a mechanism to calculate an unknown resistance using the known relationships given through the resistivity correlation to length. It demonstrated how to set-up a Wheatstone bridge and how to manipulate a Wheatstone bridge in a laboratory setting. In addition, the lab provided a demonstration of the aforementioned linear relationships. Although significant error existed in this lab, the results still reflect the relationships governing the Wheatstone bridge sufficiently for understanding in an experimental contextual environment
unknown resistance using the known relationships given through the resistivity correlation to length.It demonstrated how to set-up a Wheatstone bridge and how to manipulate a Wheatstone bridge in alaboratory setting. In addition, the lab provided a demonstration of the aforementioned linearrelationships. Although significant error existed in this lab, the results still reflect the relationships
governing the Wheatstone bridge sufficiently for understanding in an experimental contextual
environment
What is the use of the four probes in the band gap determination by four probe method?
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What is the effect of the op amp in the circuit?
So long as you remain with the range of the device (power supply rails less a volt or two), the output of an op-amp will go to what ever value is required to maintain the input stages (bridge) to remain the same. So, the effect on input voltage on output of an op-amp is dependent on the feedback circuit.
Why was 120V chosen as the standard voltage of homes in the US and not some other voltage?
The reason that 120v service was chosen, was economic. Originally electricity was delivered to homes, and most businesses, for a single purpose and that was lighting. Can openers, TVs, washers, dryers, electrical factory machinery, etc. came later. At the time the most cost effective form of light bulb was a carbon filament bulb that operated best (optimally) at 100v to 110v. This, adjusted for transmission voltage drop, set most supply lines at 120v.
Supplemental and Related Information:
By the time cost effective, and higher voltage, metal filament bulbs were brought to the market, most of the cities in the USA were already running 120v supply lines. Europe was just starting such systems and opted for higher voltage supply lines.
Higher voltages are used for long distance transmission and power distribution because more power can be transferred over the same size wire at a higher voltage (lower current). Power generation plants often use voltages in the hundreds of thousands, 115,000 to 165,000 of volts to move power over long distances. For lines of up to 20 miles long around a city, 2400 volts works well to reduce the voltage loss in the wires.
In North America, the electrical power lines going to residential streets and roads are operated at a primary voltage of 7200 volts. This voltage (12500/1.73 = 7225) is one leg from a three phase 12500 volt primary line. On the secondary of the transformers it is center tapped to provide 120 volts from each 240-volt leg to the center point. The center point is electrically neutral. The actual measured voltage in your house receptacle circuits will normally be 110 to 120 volts. All appliances are rated for the minimum operating voltage (110-115). This is the cause of confusion about the actual level of the supply voltages.
Different nominal voltage level and frequency standards are used in different countries. Europeans - and many other countries around the world - use 50 Hz (cycles per second) as the alternating frequency, not 60Hz as is used in North America and, again, many other countries around the world. The reason to use a higher voltage is that it is more economical because the current is less, so the wires can be smaller. On the other hand, the reason to use lower voltage in homes is safety: the lower the voltage, the safer it is.
If you have 10 amps drawing on one leg of your 240/120 service, and 10 amps on the other leg, the I2R losses are one fourth what they would be if you had 20 amps on just the one leg.
The Europeans use 415/240 (415/1.73 = 240), so their I2R losses are 1/16th of our 120 volt losses, with 20 amps drawing on just one leg.
480 V center tapped (split phase) is used in the UK only rarely, typically in rural areas to supply an isolated small group of houses that can be fed off a single phase overhead spur. Most houses and small businesses are supplied with 240 V single phase taken from a 415 V three phase local system, fed from a transformer of up to 700 KVA connected to the 11 kV distribution system. The voltage is mostly 240 V but is nominally described as 230 V with a suitably wide tolerance, to comply with European standards.
Originally, the service voltage was about 90 volts direct current, which was Edison's plan. Tesla proposed that the electrical grid be alternating current (AC) and competed with Edison for the first generating plant to be built in the State of New York at Niagara Falls. Edison proposed a DC system and Tesla an AC system. History tells us that Tesla won the competition, and because of that the industrial revolution was quickly accelerated. Had Edison won we would probably still be in the dark ages because of the inefficiency of transmitting DC current over long distances. While Edison was promoting the electrical light bulb around the country, almost every town required its own generating station because DC would lose so much in the transmission that it became unusable after only a couple of miles.
Tesla also had invented the poly phase alternating current generators that provided for the ability to generate the voltages necessary for long distance transmission. Tesla kept the voltage about the same as what Edison started but raised it to the 110 volts alternating current (VAC) because of the higher related voltages of 220 VAC and 440 VAC, which were integral to the more efficient poly phase generators.
The standard voltage available in most parts of the country (US) is now nominally 120 VAC volts +/- 10%, and can vary from 108 VAC to 132 VAC. It's usually around 117-118 VAC.
Transmission distances, the actual power needed in a neighborhood, cost, efficiency and safety issues dictate service parameters. Common distribution voltages run up to 16,000 volts. 12,000 is very common but there is still a lot of activity adding on to legacy distribution grids at lower voltages. A 2400 volt primary is very low for a distribution transformer.
In actuality power transmission is over many miles and the transmission voltage is more then 110kV. In fact interstate transmission is in the range of close to 500kV. At a substation it is reduced to 16kV for local area distribution. Transmission for the whole of the grid in North America is all tied together . Why? For economy and reliability. For example in the Summer some states do not use air conditioning but in Las Vegas, Nevada they do, so they actually buy the power from Canada in the summer because it is cost effective and reduces the need for more generation plants. Even then reserve spin power must be sustained for peak demands. Because power plants cannot produce near instant acceleration to meet new demands. In many cities and other peak demand areas, specialist peakers work to ensure that the the integrity of the grid is always maintained. 240 v is standard for the USA but only one phase is used and the transformer center tap is grounded, making it safer. Also, the main frequency of 60 Hz produced by power generation is not as stable as some people think. It varies throughout the day as loading changes but the controllers must legally ensure that it averages 60Hz over a complete day so that electric clocks using synchronous motors remain accurate.
Why do you measure emf with a potentiometer not with voltmeter?
EMF (E''electromotive Force'') is another term for Volts, hence the E in electronic formulas and EMF is measured with a volt meter. A potentiometer is not a meter at all, it is a variable resistor
What is the wattage in the circuit?
wattage is voltage and amperage multiplied. example V/A=W or 120v x 20a=2400 watts
What is the importance of threshold voltages and how does it work in a circuit?
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Give the derivation of Single tuned and double-tuned circuit?
The circuit has one inductor and capacitor connected in such a way that it produce the resonance condition for only one frequency. on the other hand for double tuned circuit it has more number of reactive elements and it has two tuning frequency. The single tuned circuit is of interest when the poles are imaginary, and rest of the two cases are not more interest. w=wn the time it produce the resonance and the damping factor zeta is zero and the circuit is in undamped condition.
Why is electroplating always done with direct current rather than with alternating current?
Because you want the deposited metal to stick onto the base metal that you are electroplating, i.e. the ions flow from one electrode to the other. and for that, the flow of the current has to be in a single direction, as it is in DC. in AC, the flow alternates periodically, and you will not have any deposition at all as the ions may just go back and forth.
How is sinusoidal signal produced?
You may use a filter which will round off the square pulse to sine wave.The higher order the filter the better the SINE wave . The Square pulse and the sine wave must both be tuned to our required frequency
What are three components needed for a circuit to work?
Three things that are needed to have an operating electrical circuit are:
1. Electric potential difference or voltage.
2. Conductive path, which allows the movement of charges such as wire.
3. Resistor, which acts as an electrical resistance and loosely defines any object that uses electricity to do work.
Why using wheatstone bridge in transducer?
You use a transducer in a wheatstone bridge. The wheatstone bridge allows you to find an unknown resistance.
What is the purpose of a transistor in a circuit?
A transistor has three leads, called the base, the collector, and the emitter. The voltage of the base (in relation to the ground) determines whether and how much current flows from the collector to the emitter. An NPN transistor can be off, meaning that there is no (or very little) voltage from the base; partly on, meaning that there is some voltage from the base; or saturated, meaning that it is receiving full voltage from the base. A saturated transistor allows the current to flow from the collector to the emitter unopposed; a partly on transistor provides some resistance; and a transistor that is off provides full resistance. A PNP transistor is similar to an NPN transistor except it performs the opposite function: when it is saturated, the current is fully resisted; when there is no voltage from the base, the current is not at all resisted; and when it is partly on there is some resistance.
In sum, a transistor controls the flow between the collector and the emitter based upon the voltage of the base. this is carbage. a transistor is basicaly two diodes back to back base being common TO BOTH DIODES because of inpurity doping on purpose at the depletion region the transistor will control the current flow on the other diode. Once it reaches saturation both diodes conduct therefore current can flow in BOTH DIRECTIONS ACROSS IT.
