Electrical Engineering

A single wattmeter can measure power due to one phase only. But circuit arrangements , popularly called:

1) 2-wattmeter method (requiring two wattmeters)

2)3-wattmeter method (requiring 3 wattmeters)

can be used for measuring power inn 3-phase circuit. The details of these method can be found in any standard book on electrical engineering.

First to the stop, first to go. Yield to the left. Absolutely WRONG 4 ways means you must stop and proceed one at the time safely. It has nothing to do with first or last. There maybe one car on each stop and a long line to one stop sign it means you must wait your turn until it is your turn to safely proceed.

A: The use is for transferring 8 bits of data from a parallel source into a 3 state bus Since it is 3 state 8 bits "D" flip flops it has an output control qt pin 1 if hi the flip flops are no care or floating in the 3 state

Reverse polarity is the opposite of normal polarity. Normal polarity in electronics is when you have the positive hooked up to the positive terminal and the negative to the negative terminal. Reverse polarity would be having the positive hooked up to the negative terminal and the negative to the positive terminal. The same concept can be used with magnets.

No, Terminal voltage of a battery can't be zero. For example, if my mobile's battery is at low charge. It is showing only one point of charge on screen, but there will be no fluctuation on its screen, all the other features like audio, video, display will remain same unless it will become fully out of charge. Charge could be zero but the voltage can't be zero.

Well, actually the terminal voltage of a battery can be zero, but only when the battery is totally dead and unable to take a charge (if it was a rechargeable type battery). At this point it must be disposed of.

One exception is wet cell batteries (like lead acid), if the liquid electrolyte is removed the terminal voltage goes to zero but the battery is still good and can be restored to normal operation by refilling it with electrolyte. In fact wet cell batteries are often sold fully charged but with no electrolyte and their terminal voltage is thus zero on the store shelf until the salesman fills them with electrolyte.

A liner load an electical decive that is characterized by a uniform rise and drop in current and volatage when connected in circuit. For example steady pattern can be observe when the decive is operating in a circuit.

Power requirements are measured in KVA, which stands for Kilo-Volt-Amperes. To calculate the amount of power you require you would use the following formula.

KVA = Volts * Amps / 1000

opamp is a device used to amplify ac as well as DC input signals.

It is called as operational amp becoz it is used to perform all mathematical operations. Symbol of opamp indicates the direction of current.

I guess Vc=VmSinwt;

Here Vm=Peak Voltage

Vdc=Vm/(2^.5)

Then We Calculate the Impedence of the Circuit.i.e.

Z=(R2+(XL-XC)2).5

Now Idc=Vdc/Z

This is the formula for obtaining Direct Current from Alternating Current.

AC motors are not suitable for tape recorders because the speed can not be kept sufficiently constant. Tape recorders use dc shunt-wound motors with electronic speed control.

generators have two types of winding ,

* at armature also called armature winding( winding around shaft , we can say), which is the moving part. note that armature also consists of magnets along with windings. hence produces field arount it.

* and at stator also called field winding, because when armature rotates its flux(field) is cutted by the stator windings and produces mutually induced e.m.f in it( in stator windings off course) causing current to flow.

this current also produces some electric field around it which is in return cutted by the armature windings hince a little amount of e.m.f ( also called back e.m.f) produced in armature due to stator winding current.

know this current in armature (due to back e.m.f produced by stator winding) produces additional field , hence causing more current in stator winding. this is the reason that why stator windings are called field winding( as they cause electric field of armature stronger and cause more current in output).

note that out put is taken from the stator windings in generators.

A diode mainly consists of only 2 terminals(anode,cathode).A SCR mainly contains one more terminal called GATE.The main purpose of the gate in an SCR is just to provide pulses.The main draw back of SCR is it is not fully controllable device.

This occurs due to a sudden "cut-off" or suspension, or release of voltage. Sometimes this can even cause a breaker to trip, or a GFI unit to trip, due to the sudden spike.

A2.) As a magnetic field collapses it induces currents in conductors nearby.

The faster the field collapses the higher the voltage.

This applies to inductive circuits. Although an inductor (coil) may not be physically present in any particular circuit, there is always inductance present, by the very wires themselves.

All electrical circuits have reactive components - parts of the circuit that hold charge, such as inductors and capacitors. When switching these elements out, the charge they are holding cannot instantly go to zero; it's released in the form of a spike. When switching these elements into a circuit, a sag can result due to these elements attempting to absorb power. Switching in can also result in spikes due to the capacitive and reactive elements creating a "tank" circuit (the voltage will sag slightly, then spike). At their resonant frequency, the reactive and capacitive elements will cause voltages to spike signficantly (for more information, look up LC tank circuits). Similarly, switching out can result in the trapped energy between capacitive and reactive elements to pass back and forth at a resonant frequency, spiking the voltage.

It is a step up transformer since the secondary windings are greater than the primary.

the turns ratio is (primary to secondary) 1:5, so the primary voltages is 1/5 of the secondary (5 volts).

The power P dissipated by a resistor will leave the resistor in the form of thermal energy (heat). It will get hot due to the fact that the material it is made of opposes current flow, and when current is forced through it by a voltage source, it gets hot in response. Resistance R could be thought of as "electrical friction" in many cases. Resistance is measured in ohms, voltage V in volts and current I in amperes (amps). The power in watts dissipated by a resistor with the value R will be the square of the current through it times its resistance. P=I2R The power in watts dissipated by a resistor with the value R will be the square of the voltage drop across it divided by its resistance. P=V2/R Because E means energy we take V for voltage. The power in watts dissipated by a resistor with the value R will be the voltage drop across it times the current flow through it. P=IV All three statements are true, and they all say the same thing. The mathematician might say that the variable P is being expressed in terms of the variables I, V and R. As all the statements are true, it can be said that P=I2R=V2/R=IV.

There are two types of voltage:

1. AC

2. DC

It's hard to answer what 'Types' of voltage there are. It is measured in volts and can span anywhere from zero to almost infinity.

Useable voltages can be roughly zoned.

From zero up to 1 volt. = Signal voltage.

1.5v to 36v = Low voltage for electronics and consumer items.

48v to 240v = High voltage for domestic applications in the home.

280 to 512v = High voltage used for industrial machines.

1KV to 400Kv= Very high voltage for transmission over distance.

AC (Alternating current) is made using a spinning generator. It is the only type of current that can be transformed easily from one volktage to another using a transformer.

DC (Direct current) is normally made using batteries, but can also be made using a generator with a commutator and brush gear.

Very hard to change voltage, but useful at low voltages for electronics.

dc means deccan chronical news paper agency in India.

Ph

such a three phase is 3Ph

for example

You use a megger. This allows you to check what the condition of the insulation of the motor windings are. An ohms check on each phase should be an easy way if it reads OPEN then there's your bad phase. Otherwise there are diffrent types of 3 phase motors, could be the brushes, commutator, sliprings, many many things.

I read that it can go up to 80 Volts, any more and it becomes a shock hazard to the operator.