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How many times per second does the alternating current generated at large power?
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∙ 13y ago
120
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∙ 14y ago
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Why do transmission lines use alternating current?
Transmission lines use alternating current in order to support stepping-up and stepping-down of the voltage with transformers. Voltage is stepped-up at the power station, sent over the transmission lines, and stepped-down at the receiver. (This is a simplified explanation.) By stepping-up, you reduce the current carrying requirement of the lines, and they can thus be smaller.You could not do this with direct current as transformers only work for alternating current.
Why does the induced emf known as back emf?
In a dc motor the voltage generated in the armature acts against the supply voltage. The current is the voltage difference divided by the armature resistance. If the rotor is turned faster so that the back emf exceeds the supply voltage, the current goes the other way and the motor has become a generator.
What is designed to use a small current to control a large current?
A silicon controlled rectifier falls into this category.
What kind of output current comes in the generator?
Direct current is simply a by-product of the generating process. It simply means the current travels in one polarity, where as AC, or alternating current changes polarity at a constant rate. (60 hertz in the US)
Why can we start a shunt motor under no load but why can't a series motor?
The torque on a series motor is determined by the square of the armature current and, so, is very large -much larger than that of a shunt motor. Consequently, on starting, with no back-emf being generated, the torque on a series motor can be dangerously high if the machine has no mechanical load.
How many times per second does the alternating current generated at large power generator reverse directions?
120
Why is alternating current used for domestic purposes?
Alternating current is easier to distribute than direct current, because alternating current can be raised or lowered in voltage by a transformer. This allows very high voltages to be used in long distance transfer of electricity, which is then stepped down several times before being supplied to the end user. As the voltage is increased in a circuit, the current, as measured in amperes, decreases for a given load. This allows the use of lighter wire to transmit large amounts of electricity.
Absolute refractory period relative refractory period?
In absolute refractory period, none of channels are reconfigured, so that second active potential cannot be generated no matter how large the stimulus current is applied to the neuron. In contrast, in relative refractory period, some but not all of channels are reconfigured, another action potential can be generated but only by a greater stimulus current thatn that originally needed.
Why do transmission lines use alternating current?
Transmission lines use alternating current in order to support stepping-up and stepping-down of the voltage with transformers. Voltage is stepped-up at the power station, sent over the transmission lines, and stepped-down at the receiver. (This is a simplified explanation.) By stepping-up, you reduce the current carrying requirement of the lines, and they can thus be smaller.You could not do this with direct current as transformers only work for alternating current.
A lamp is connected to a battery if a capacitor is inserted in the positive wire between the battery and the lamp what will happen?
large capacitors will become charged in a fraction of a second if a DC voltage is applied to its terminalsonce a capacitor becomes fully charge it acts as an open circuit to direct current in other words, once the capacitor charged by a DC voltage, the current will cease to flow in the branch of the circuit which contains the capacitor.a capacitor also offers opposition known as (capacitive reactance) to alternating current. it does not , however ,act as an open circuit to when an a-c alternating current voltage is applied.
What is DC power?
Direct current (DC or "continuous current") is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also be through semiconductors, insulators, or even through a vacuum as in electron or ion beams. In direct current, the electric charges flow in the same direction, distinguishing it from alternating current (AC). A term formerly used for direct current was Galvanic current. Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be made into alternating current with an inverter or a motor-generator set. The first commercial electric power transmission (developed by Thomas Edison in the late nineteenth century) used direct current. Because of the advantage of alternating current over direct current in transforming and transmission, electric power distribution today is nearly all alternating current. For applications requiring direct current, such as third rail power systems, alternating current is distributed to a substation, which utilizes a rectifier to convert the power to direct current. See War of Currents. Direct current is used to charge batteries, and in nearly all electronic systems as the power supply. Very large quantities of direct-current power are used in production of aluminum and other electrochemical processes. Direct current is used for some railway propulsion, especially in urban areas. High voltage direct current is used to transmit large amounts of power from remote generation sites or to interconnect alternating current power grids.
Does the light switch use direct current or alternating current?
A direct current flows only in one direction. An alternating current changes its direction of flow in a regular (cyclic) way, all the time and usually several times per second.Other answersAn alternating current (AC) is an electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant.The usual waveform of an AC power circuit is a sine wave, as this is the way the electricity is generated in the power plants. It also allows us to efficiently transmit the energy by transforming it to a higher voltage.Alternating current is an electrical current whose magnitude and direction vary cyclically. The direction of direct current remains constant. The frequency of the electrical system varies by country. Most electric power is generated at either 50 or 60 Hertz (cycles per second).In electronic equipment, different waveforms are used, such as triangular, sawtooth or square waves, the latter form being the "heart and soul" of digital computers and modern communications.During just one cycle of a single-phase alternating supply, the "live" or "hot" wire of an alternating voltage (or current) supply goes from zero to its positive peak, then back to zero, then continues on to its negative peak and back to zero again.These positive- and negative-going parts of each cycle are always voltages (or currents) relative to the "neutral" wire. A neutral wire is necessary to allow the currents to return to the alternator.In a 60 hertz supply there are 60 such cycles in each and every second. Similarly, there are 50 such cycles in each and every second in a 50 hertz supply.The voltage in the "live" or "hot" wire usually follows a waveform very close to a perfect sine wave.Depending on the voltages and currents required, alternators can be, for example, very large power generating machines installed at power stations or the much smaller type of alternators which are fitted into vehicles.AC, or Alternating Current, does exactly what the name implies. In USA, Canada - and in other countries which use the same service frequency - the direction of the current changes 60 times a second (also called a frequency of 60 Hertz) between the 'Hot' (also known as the 'Live') wire - often colored Black - and the Common (also known as the 'Neutral') wire, which is usually colored White. In Europe and many other areas of the world, the service frequency is 50 times a second (50 Hertz).It is the service frequency which makes the typical "humming" sound you hear from transformers or electric AC motors when they are running.The good link below "AC, DC and Electrical Signals" gives a lot more information about the difference between alternating current and direct current.Direct Current and Alternating Current:The first and simpler type of electricity is called direct current, abbreviated "DC". This is the type of electricity that is produced by batteries, static, and lightning. A voltage is created, and possibly stored, until a circuit is completed. When it is, the current flows directly, in one direction. In the circuit, the current flows at a specific, constant voltage (this is oversimplified somewhat but good enough for our needs.)The other type of electricity is called alternating current, or "AC". This is the electricity that you get from your house's wall and that you use to power most of your electrical appliances. Alternating current is harder to explain than direct current. The electricity is not provided as a single, constant voltage, but rather as a sinusoidal (sine) wave that over time starts at zero, increases to a maximum value, then decreases to a minimum value, and repeats.
What is meany by resistor?
Resistor is a component of an electric circuit that resist the flow of direct or alternating electric current . It can also limit or divide the current, reduce the voltage, protect an electric circuit, or provide large amounts of heat or light.
What is the absolute refractory period?
Absolute Refractory Period:It is the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.ORAfter repolarization there is a period during which a second action potential cannot be initiated, no matter how large a stimulus current is applied to the neuron. This is called the absolute refractory period, and it is followed by a relative refractory period, during which another action potential can be generated
How can a 12 volt battery inverter give power to a house?
An inverter converts direct current into alternating current. An inexpensive 12 volt inverter is often used to convert 12 volt direct current from a battery to 120 volt alternating current to power small household appliances during a power failure. More expensive inverter systems with large batteries are also available for use with solar panels, wind generators, or other non-commercial power sources.
When are alternating currents commonly used?
The electrical power that the public utility company delivers to you via the wall outlets in your house is supplied in the form of alternating voltage, which produces an alternating current through any device you plug into one of the outlets.
Why are windmills so large?
The larger the windmill, the more power can be generated.
