In short circuit test very low voltage at primary approx 5 % of the rated voltage is given and secondary is short circuited by an ammeter. Due to low voltage very low flux is developed in core of the transformer and due to that iron losses are very low which can be neglected.
actually it is operated at (10-15)% of the rated voltage and as you know n case of low voltage low magnetic flux is produced and then there will be low magnetic field density(B). and we know hysteresis and eddy current losses depend on (B).as in case of :
hysteresis depends on B^1.2 and
eddy current depends on B^2
So if B is low then both losses(collectively called constant losses) will be very very low.
These recommendations depend on the height and size of the room, the season, and the activity taking place in the room.
Keep in mind that warm air rises to the top and cold air settles on the bottom. Air settles in layers from warm at the top to cold at the bottom, if left alone at equilibrium.
Ceiling fan recommendations:
In the winter
Set the fan to run counterclockwise (reverse; this looks clockwise as you are looking up). This will redirect the warm air from the ceiling and down the walls and into the living space where the people actually are. In a house, you would run the fan at a low speed so that you don't actually cool the warm air that you are moving downward. If you have a high ceiling, or are trying to heat a hall or a church, you may want to increase the fan speed so that the warm air will reach the living space as long as the fan speed does not create an unwanted downdraft at the people below.
In the summer
In a room of normal height (8 - 10 ft), you should operate your fan so that it turns clockwise (this looks counterclockwise as you are looking up), causing a more directed downdraft, especially with the fan running slightly faster. This causes a wind-chill effect because the skin evaporates slight amounts of water from the sweat glands and thereby provides cooling through the skin's surface. However, the air is only moved but not cooled! You may find that you can turn your thermostat down a degree or two and save more money on energy costs. The air blowing down won't actually cool the room though, so you should turn the fan off when there are no people (or animals) in the room.
In a high hall or church
It may be best NOT to run the fans at all in summer. This lowers the demand for cooling since the hot layer on top is an excellent insulation between the cool air near the floor (and the people) and the hot roof and outside.
A large, tall manufacturing hall would typically have different goals. There one would have a floor full of heat producing machinery plus the people operating it, working hard and welcoming a bit of a breeze. Then it would make sense to run the fans at fairly high speed to create a certain and directed downdraft. And with the shifts going throughout the days of the week, the fans should be running all the time and maybe in all seasons.
Finally, fans typically use 80-100 watts. When used properly, ceiling fans can really help to optimize the comfort level of the people and save energy and money.
Another user contributes this:
The important point from the previous answer is that fans are for cooling people. Advanced Energy (see the Related Link) says: "The most optimistic estimates I've seen on energy savings from ceiling fans peg the air conditioning savings at about 15%, assuming people do raise the thermostat setting and only run the fans when people are in the room, and taking into account the cost of energy used by the fan itself."
yes lenz law states that every current opposes the reason which cause the generation of that current . it is very useful for considering back emf in dc motor.
The lenz law also help us to determine the supply voltage of DC motor.
The instrument used to measure electrical current is called an ammeter, which is actually a shortened form of 'amp meter'. The current is measured in amperes. In scientific labs, a much more sensitive instrument called a galvanometer is used to measure very small currents.
Ohm's Law states: "The current flowing through a conductor is directly proportional to the applied voltage, provided the temperature of the conductor remains constant."
It specifically refers to conductors and not resistors. And it takes into consideration the need to maintain a given temperature as the voltage and current vary. At the time, Georg Ohm already knew that allowing the temperature to vary would break the constant ratio.
Keep in mind that this was a historic new understanding that he had discovered was applicable to various conductors (metals).
Ohm's Law is by no means a universal law, and very few materials or electrical components actually 'obey' Ohm's Law. Those that do (some metals) are termed 'linear' or 'ohmic'; those that don't (most) are termed 'non-linear' or 'non-ohmic'.
Simply put, if the graph of voltage against current, plotted for variations in voltage, is a straight line, then Ohm's Law applies; if the graph is not a straight line, then Ohm's Law does not apply. And very few materials/devices produce a straight line graph. Based on this, you could say that 'Ohm's Law' is not a 'law' at all, but simply describes the behaviour of a limited range of materials.
So Ohm's Law doesn't apply to heated metals such as tungsten filaments, or to circuit components, such as diodes and to practically all other electronic devices.
The basic unit of electrical resistance was given the name 'The Ohm' in honor of Georg Ohm. The symbol for the unit is Î©, pronounced Omega. The ratio of a given voltage to resulting current will always tell us what the resistance happens to be for that particular instance. This is because the ratio of voltage to current is, by definition, resistance - however, this has nothing whatsoever to do with Ohm's Law, but is simply a definition of resistance!
E = I R
Voltage = Current times Resistance
As the alternate answers below clearly indicate, there is a widespread misunderstanding regarding Ohm's Law. Answer Resistance defines the relationships between (E) electromotive force in Volts and (I) current in Amperes. One ohm is defined as the resistance value through which one volt will maintain a current of one ampere. In other words, an ohm is a volt per ampere.
(I) Current is what flows on a wire or conductor like water flowing down a river. Current flows between points of different voltage. Current is measured in (A) Amperes, abbreviated: amps.
(E) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in Volts.
(R) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in Ohms.
Answer The statement taught in electrical training is "Current is directly proportional to the applied EMF and inversely proportional to the resistance of the circuit".
Ohm's law: When there is a potential (Voltage-V) different between two ends of a conductor a follow of charges will be created (The current-I) through this conductor which is directly proportional to the voltage difference and inversely proportional to the resistance of the conductor (Resistance-R ).
I Î± Vdifference
I Î± 1/R
I=Vdifference/R : Current increases with increase of voltage, but decreases with the increase of the resistance
Answer Ohms Law states that the amount of current that passes through an object is directly proportional to the potential voltage across that object, and inversely proportional to the resistance, or electrical impedance, of that object. In other words: * as voltage goes up, the current goes up by the same proportional amount * as the impedance goes up, the current is reduced by the same proportional amount. Ohms Law can be stated mathematically as:
I = E/R Where: I is the current, E is the voltage, R is the resistance
As you can see from the above formula, if the voltage were to double, then so would the current. If the resistance were to triple, then the current would be one-third of its former value. You can use Ohms Law to calculate any value if you know the other two. These are expressed mathematically as: V = I x R (to calculate Voltage) R = V / I (to calculate Resistance) In the above calculations, V is measured in 'volts', I is measured in 'amperes' (or amps), and R is measured in Ohms.
Ohm's Law states Voltage = Current x Resistance. Except in unusual circumstances the resistance "R" is a constant. When you increase voltage, current increases.
Ohm's Law states that 'the current flowing through a conductor at constant temperature is directly proportional to the potential difference across that conductor'.
Ohm's Law is by no means a universal law, and onlyapplies to those conductors or devices where the ratio of voltage to current is constant over a wide range of potential differences. These materials are termed 'ohmic' or 'linear', whereas those materials and devices that do not obey Ohm's Law (and there are a great many!) are termed 'non-ohmic' or 'non-linear'. Examples of non-ohmic materials and devices include tungsten (lamp filaments), diodes, electrolytes, etc.
The ratio of voltage to current is termed resistance (R = E/I), and is derived from the definition of the ohm, and not (as many people think) from Ohm's Law. This equation can be applied to both ohmic and non-ohmic materials and devices, so applies whether or not Ohm's Law is followed.
The Current-Voltage relationship of a diode is not constant (not a straight line) and hence the resistance cannot be measured. Due to this non-linear nature of the the curve, there exists a unique value of resistance at every point of the curve which is called dynamic resistance (not static of constant resistance).
The dynamic resistance equals the change in voltage divided by the change in current, when the voltage is changed by a small amount. In other words it is the slope of the graph of voltage against current. The dynamic resistance is different at different current values.
About 30 years ago, and I do not remeber the brand or maker, there was a digital multimeter that DID measure dynamic resistance in diodes. It was a God Send for testing diodes in circuit. Diodes only conduct in one direction, so the device would show an open in one direction and a resistance under 1000 ohms on the other or a short (0 ohms).
Inductive load power is reactive, it is given by the formula:
in time domain (instant power);
in Laplace transform domain (RMS denotes root mean square amplitude).
VL is the voltage across the inductor L and IL is its current (current enters in the "+" voltage reference pin, by applying user convention in which absorbed power is positive).
Power is reactive since voltage and current are always in quadrature:
VL(s) = s L IL(s),
in Laplace domain (derived from the time-domain formula vL(t)= L diL(t)/dt).
A real-life inductor will also show an active power term, which arises from parasitic resistance non-ideality; it can be modeled as a resistance DCR in series with the inductor itself:
An inductive load such as an induction motor draws power from the supply with a power factor of less than 1.
Power = voltage x current x power factor.
This happens because the current reaches its peak in the ac cycle after the voltage, so that for a small part of the cycle power flows back into the supply from energy stored in the motor's internal magnetic field. The time-lag is measured in degrees and called the phase difference. 360 degrees denotes one complete cycle.
The power factor is the cosine of the phase difference, so that (for example) a resistive load has no phase difference so that the power factor is 1, while for a pure inductor the phase difference is 90 degrees and the power factor is zero.
If the rms voltage and current are expressed in complex-number form, also known as vectors or phasors, the real power is the real part of VI*, where the asterisk denotes the complex conjugate.
Another way to calculate the real power is to calculate the average value of the instantaneous power V x I. If the voltage is Vcos(wt) and the current is Icos(wt+phi) then those expressions can be multiplied together and trigonometry formulas used to show that the power factor is cos(phi) as stated.
Real power is measured from the average value of volts times amps with an instrument that contains a voltage coil and a current coil. The force produced is equal to the instantaneous power, and the instrument measures its average value muliplied by the time.
A: Hissing is because is overheating before it destroy itself. But other noises are caused by loose lamination of the core.
B: Hissing noise is produced due to this reason but here is another important point is about frequency (e.g for 50 Hz) the core lamination face attractive and repulsive forces fifty times in one
cycle because frequency is 50 Hz.
The original answer is unnecessarily melodramatic. Transformers are fitted with protective devices that will disconnect the transformer long before a rise in temperature will cause it to 'destroy itself'!
'Hissing', as opposed to 'humming', is usually caused by the ionisation of air in the immediate vicinity of the transformer's high-voltage bushings (hollow insulators). This also manifests itself, after dark, as a blue-coloured luminous discharge.
'Humming', on the other hand, is due to something called 'magnetostriction', a distortion to the core laminations -exactly as described in the original answer, except that the attractive/repulsive forces are twice that of the supply frequency (i.e. 100 times, in the case of 50 Hz), together with harmonics based on that frequency.
50 Kv = 50,000 volts
Martin Cooper invented the cell (mobile) phone. He was the first one to make a call and speak on his moble phone.
Mr Cooper, born December 26, 1928, wanted people to be able to carry their phones with them anywhere. While he was a project manager at Motorola in 1973, Cooper set up a base station in New York with the first working prototype of a cellular telephone, the Motorola Dyna-Tac. After some initial testing in Washington for the F.C.C., Mr. Cooper and Motorola took the phone technology to New York to show the public.
The First Cellphone (1973)
Name: Motorola Dyna-Tac
Size: 9 x 5 x 1.75 inches
Weight: 2.5 pounds
Number of Circuit Boards: 30
Talk time: 35 minutes
Recharge Time: 10 hours
Features: Talk, listen, dial
See related links for further information on Martin Cooper and his invention.
The idea of the cell phone began in the 1920's with police radios, but it wasn't until 1947 that the first one was made by Bell labs. In 1974 Dr. Martin Cooper is given credit for the cell phone that is most like the ones we have today. He was working for Motorola at the time. The phone was only for government use and in 1984 it was sold to the public for the first time. The early cell phones were large, heavy, and copied land line phones in style. They were carried in a zippered bag with the whole bottom as the battery.
The cell phone was first thought of in the 1920's when the use of police radios began. In 1947 Bell Labs made the first cell phone, but it took Dr. Cooper of Motorola to make a cell phone in 1974 for the government. The public use of cell phones began in 1984.
Your question has two answers. The phone was invented in 1889 by Bell. The cell phone idea began in the 1930's, but in 1947 Bell Labs made a cell type phone. The first cell phone inventor id given to Dr. Martin Cooper of Motorola in 1974. This phone was sold to the government. The public did not get it until 1984.
It was made by Bell labs in 1947, but the man given the most credit for it is Dr. Martin Cooper who made one very much like what we have today in 1973.
We knew someday everybody would have one. Martin Coopercreated the "DynaTAC," the first commercial cell phone, which hit the market in 1983. (CNN) -- In 1973, Martin Cooper changed the world, although he didn't know it yet. With the invention there was concern regarding brain cancer due to the fact that cell phones send out high frequency of radio waves.
It was invented by Will Maacmillan in 1969
Doctor Martin Cooper invented the modern cell phone. He invented the technology responsible for the cell phone when was the Director of Research and Development at Motorola. Cooper is also known as the first person to make a call on a cell phone. His groundbreaking call took place in April of 1973 in New York. He is currently the CEO of an antenna corporation.
Logic gates are in fact the building block of digital electronics; they are formed by the combination of transistors (either BJT or MOSFET) to realize some digital operations (like logical OR, AND, INVERT ). Every digital product, like computers, mobile, calculators even digital watches, contain logic gates. The use of logic gates in digital world can be understood better by the following example: the single bit full adder in digital electronics is a logic circuit which perform the logical addition of two single bit binary numbers (a,b,cin) a and b are the the two binary number of single digit (either 1 or 0) and cin is the carry input . say for example a,b,cin= 1,1,1 gave an logical sum output of 1 and a carry of 1 , a,b,cin= 110 gave sum= 0 and carry of 1. Now this adder can be formed by the combination of many gate like by using NAND gates only. or by using XOR , AND ,OR gates and so on. So, in a nutshell, the adder which is of great importance in your computer processor and also in many more applications is basically built from the logic gates.
The Indian electronics system design and manufacturing (ESDM) industry is at a huge inflection point. From being predominantly consumption-driven, the Indian ESDM industry holds potential to become a design-led manufacturing industry. Concerted efforts from both the government and the industry are required to propel the Indian ESDM industry into one of the critical GDP contributors soon. ndia Electronics and Semiconductor Association (IESA), the trade body, representing the Indian electronic system design and manufacturing space, in collaboration with Markets And Markets, on Tuesday, launched an industry report on Indian semiconductor fabless startup ecosystem at its annual Vision Summit. The report was launched by Ashwini K Aggarwal, Chairman, IESA; Anilkumar Muniswamy, Director, SLN Technologies Ltd. and Jitendra Chaddah, Chair, Fabless CIG and Senior Director, Strategic Relations and Operations, Intel India on Day 1 of Vision Summit.
A motor converts electrical energy into mechanical energy and a generator converts mechanical energy into electrical energy.
The primary difference between a motor and a generator is that one converts electrical energy into mechanical energy (that's the motor) and the other converts mechanical energy into electrical energy (that's the generator).
In some cases of direct current (DC) machines, but not alternating current (AC) machines, there is so little difference that a single device (it might be called a motor-generator) can be used as either a motor or a generator.
A superb example of this would be the motor-generator that is used in electric vehicles: when the vehicle is accelerated, the batteries supply power to the motor-generator and it acts as a motor, driving the wheels. When the brake is applied, the motor-generator shifts function and the vehicle's inertia is used by the motor-generator to generate electricity and put some energy back into the batteries. This slows the vehicle down. The one device (the motor-generator) is being used in either capacity. The "handle" often applied to electric vehicles with this feature is dynamic braking.
They alike because they both have stators and rotors they are different in that the generator is driven by mechanical device that rotates the rotor, the rotor cuts through magnetic force fields and electricity is generated. The motor is driven by an input of electricity into the stator and the rotor is forced to turn by reaction with magnetic force fields.
Generator will provides current to load ......... but motor will drawn current............... generator is based on Flemming right hand rule but motor is based on left hand rule.
Just to generalize,
No high output till all inputs are high.
The plural of 'ohm' is ohms, not ohm's.
The alpha-numeric code for identifying the resistance of a resistor is quite straightforward.
The letter is used as a multiplier. For example, k= x1000 and M = x1000 000. In other words, k represents kilo, and M represents mega.
The position of the letter represents the position of the decimal marker.
Coulombs are a measure of charge - literally electrons, although the whole unit is much larger than a single electron.
In some circuits, such as lithium ion battery chargers, literally measure the amount of current over time which gives you the amount of charge - coulombs - that has passed from the battery into the powered device or vice versa.
All that being said, in this case, the value of the coulombs can be negative. This simply represents a charge imbalance.
Power is measured in Watts. Power can be generated in Watts or consumed in Watts.
You cannot. It must be taken out of the circuit and then tested on its own.
That's not 100% true because, if it has wires at its ends, you can cut through one wire with an appropriate tool and then test the capacitor "out of circuit". If the capacitor is ok you can then re-join the two cut wire ends by applying a blob of solder carefully. (But, to avoid damaging the capacitor, use a suitable heat sink to shield the body of the capacitor from the heat of the soldering iron.)
With direct current a capacitor also works like a special type of resistance. Whilst being charged up, it will show low resistance. As it slowly (or quickly) charges, the resistance will grow larger and larger. Whenever I repair circuitry and I have doubts about a capacitor (in the uF area) I simply use my multimeter on its Ohms setting. If a capacitor has shorted, then the result will be 0 Ohm. If the capacitor is working, or partially working, the resistance will gradually increase until it is out of range of the multimeter.
Use an ohm-meter first to test the on-board capacitor and then use it to test a similar capacitor off-board, to see if the results sort of match up.
Most often they will not match completely as on-board you also measure the effect of all other components connected into circuit with the capacitor. It might point you in the right direction though.
On a separate thought, if you really cannot remove it, or disconnect one of its connections, then why test it at all? If it really can't be removed to replace it, then it makes no sense to test it!
A capacitor can be tested using multimeter without removing it from circuit. but in order to check it, its polarities should be noted and then keep the positive terminal of multimeter on positive of capacitor and negative terminal on negative. It is vital to note that the readings will be affected by the remainder of the circuit. To test for capacitor function in circuit demands a good understanding of the circuit operation.
Of course there are ways to test capacitors, both in circuit and out. While a truly accurate test involved taking the cap out of circuit, a basic test can certainly be done in circuit.
Out of circuit, one can either connect to a VM, or better yet, an oscilloscope, and measure the time for voltage to decay to zero across the capacitor. This time should equal the time given by the equation for the time constant, and is dependant on the values associated with that particular capacitor.
For RC circuits, this equation equals:
Ï„ = R Ã— C. It is the time required to charge the capacitor, through the resistor, to 63.2 (â‰ˆ 63) percent of full charge; or to discharge it to 36.8 (â‰ˆ 37) percent of its initial voltage. These values are derived from 1 âˆ’ e âˆ’ 1 and e âˆ’ 1 respectively.
It is important to keep in mind that one must apply a voltage across the capacitor at its rated value. Thus, if it is a 400V capacitor driving a tube amp, for instance, it must be driven at around 400V. Driving it at 12V will lead to useless results.
The only proper way to check for a capacitor value and or leakage is with a proper test bridge: set it to the capacitor's DC rating with it removed from the circuit completely. Any other way is just waste of time.
Additionally, a common in-circuit test for a electrolytic capacitor is to measure its Equivalent Series Resistance (ESR) which can be done with an ESR meter. This is a quick and easy way to locate failing electrolytic capacitors, especially in power supply circuits.
An effective method of testing any component in-circuit is with an in-circuit curve tracer. If you have an oscilloscope with X-Y input mode you can easily build one of these on your own. They do take some getting used to before you can use it effectively and are most useful for good board vs. bad boardcomparison.
A: it must apply to AC since there is no phase in DC. Since AC is a complete circle 0-360 degrees the principle if to conduct current at a degree of the circle. And AC has both positive 0 to 180 and negative 180 to 360 polarity it is possible to control output power by conducting current only at certain angle of the circle . The phase angle is to differentiate the conducting current in which quadrant of the circle
It depends. If it's an inductive ammeter (the kind that clamps around a wire), it won't work at all. If it is the type of ammeter that is actually placed in the circuit, it will work but it won't be accurate.
Actually, modern 'clamp on' ammeters WILL measure d.c. currents. It uses the Hall Effect to measure the current.
It depends on the current being drawn by the computer's components. The voltage will remain constant at 230V and should have a maximum amperage rating labeled on the power supply. Multiply the volts times the max amp rating to find out the max wattage that the power supply can handle. The watts actually being used is probably lower than the rated max (and should be).
Use either DC to Dc converter or voltage regulators for the required voltages.AnswerA common method is to use a voltage dividercircuit. This comprises a number of resistors, connected in series, across the power supply. This creates a series of voltage drops across each resistor and, by choosing resistors of appropriate value, the desired load voltage can be achieved.
For example, if three identical resistors are connected in series across 9 V, then the voltage across each resistor will be 3 V, and the load can be connected across any one of these resistors.
In practise, selecting the appropriate values of resistance is more complicated than this simple example, because (1) the resistors themselves mustn't overload the power supply, and (2) the load itself, being connected in parallel with one of the voltage divider resistors, affects the overall resistance of the voltage divider circuit and must, therefore, be taken into account when designing the circuit. This is called the 'loading effect' and, to put it simply, its effect is minimised providing the resistance of the load is VERY much larger than that of the voltage divider resistor it is connected across.
This sounds like you're trying to run a 3-volt device off a 9-volt battery. I would do it in one of three ways.
First way is if there's nothing in the circuit that needs 9 volts. Your best bet here is to replace the 9-volt battery clip with either a holder for two AAA cells or two A-76 button cells. Trying to reduce the output of a 9-volt battery to 3 volts will produce lots of heat. You'll get a fairly short battery life, too. AAA cells are about the same size as a 9-volt; button cells are way smaller. There is a 3.3-volt regulator called the 7803SR - Murata makes it - but they cost $10 each.
Second way is if you need both 3v and 9v...in that case, I would install a pair of AAA cells alongside the 9v cell and wire the 3v supply to the circuit that needs it.
And third is if this is a flashlight. In that case it's even easier: replace the 3v bulb with a 9v bulb (yes, there are 9v flashlight bulbs) and be happy.
They are words that show time or order in a phrase, for example: then, after that, at noon, next, after dinner, and so on.
Typical home use UPS devices for computers are plugged into your AC power. There is an input circuit that converts AC to DC and continuously charges the internal batteries in the UPS device. The DC output from the batteries is then converted to AC to power the computer or other device connected to the UPS. There is also a circuit that detects that the house power is no longer functioning and typically sounds an alarm of some sort.
Its 50 hertz as Ac change direction after every 1/100 second.
Its 50 HZ or 50 Cycles per second.
The standard frequency of alternating current in India is 50 Hz.
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