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What else can I help you with?
What does ballast mean?
Electricity. Also called ballast resistor. a device, often a resistor, that maintains the current in a circuit at a constant value by varying its resistance in order to counteract changes in voltage. a device that maintains the current through a fluorescent or mercury lamp at the desired constant value, sometimes also providing the necessary starting voltage and current.
Can a transformer work with d.c.?
The primary coil has to induce current in the secondary coil. The only way this can happen is if there is a varying magantic field in the primary which then will induce a varying mag field in the secondary which results in a current in the sec. Only varying current can induce a varying mag field only a varying mag field can induce current So you need a varying current in the primary. D.C. is not a varying current so it cannot induce a mag field in the coil. A.C. (it does not have to be +/- it just has to be varying) can do so.
What happens if voltage is constant and current is varying when an scr triggers?
Even if the current is varying,as long as the current reaches the value required to trigger the SCR, it will snap into operation. The SCR will remain in operation until the current through it drops to a value below the holding current.
How can the frequency and voltage of an alternator be changed?
The frequency is changed by varying its speed, and the the voltage is changed by varying its field current.
What is polarogram?
It is a plot of diffusion current as a function of varying potential or, a plot of current against applied voltage.
Is an electric voltage a varying electric current that reprsents information?
false
What is series - parallel connection?
In series connection current will be same. in parrel connection voltage will be same and current wil be varying
Why would direct current be unsiutable for transformers?
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors-the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.Transformers depend on the changing of magnetic fields within the transformer. Direct current would cause a magnetic field to form in the primary coil, but its the change that induces the current in the secondary field. the change only occurs if an alternating current is applied.
Constant voltage power supplies will maintain a constant voltage under varying?
current.
How reactive power generated?
Every electric loads that works with magnetic fields(i.e: motor,chokes,Transformers,inductive heating,arc-welding generators etc)produces a varying electric lags which is called INDUCTANCE.The lag of inductive loads maintain the current sense(eg: Positive) for some time and the negative going voltage tries to reverse it.These phase shift between current and voltages have to be maintained.The current and voltage have opposite sign.During this time the negative power or energy is fed to the network/circuit.When current and voltages have same sign again,the same amount of energy is required to built up the magnetic field in inductive loads.This magnetic reversal energy is called Reactive power.In AC circuit (50 Hz - 60 Hz) this process repeated 50 to 60 times a second.So an obvious solution is to briefly store the magnetic reversal energy in capacitor and relieve the network (the supply line)of this reactive energy.
How do you control dc voltage in alternators?
Typically by varying the magnetic field strength. This is done by varying the current flow through the field windings. It is usually accomplished by a voltage regulator circuit.
Why DC should not use in transformer?
In transformers two coils are used for mutual induction (check transformers theory) and so that the magnetic flux generated in primary coil gets transferred to secondary coil we need inductance which is only generated in case of an AC current flowing through a coil (check faraday's law).DC current has no frequency so no inductance(2*pi*f*L) so no induced emf !CommentInductance is not 'generated'; it is a natural quantity just like resistance or capacitance and is quite independent of whether the supply is d.c. or a.c. (although it can vary with the quantity of current passing through the circuit). And the equation 2 pi f L is that for inductive reactance, not inductance!Transformers are a.c. machines, because an varying current is required in order to create a varying magnetic flux around the core of the transformer. When a varying flux links the secondary winding, it induces a voltage into that winding through the process of mutual induction (not 'inductance'!). If d.c. is applied, the resulting flux will be constant and mutual induction will not occur. Furthermore, by applying a d.c. supply to the transformer, you risk the chance of burning out the primary winding, as its resistance is very low compared with its inductive reactance (opposition to a.c.), and the resulting current can be much larger than it's designed to carry.Transformers CAN work with a.c. providing the current is continously interrupted, which is the principle of operation behind a car's ignition coil.
