Electrical Engineering

Impedance is a vector sum using the formula Z = square root (XL2 + R2); where Z = impedance, XL = inductive reactance, and R = resistance. Therefor the formula for a circuit where XL = 64ohm's and R = 36ohm's is Z = square root(642 + 322); Z = 71.6ohms.

By Ohm's law, resistance is voltage divided by current, so the resistance of a light bulb can be measured by observing the voltage across it simultaneously with observing the current through it.

Interestingly, the hot resistance is significantly different that the cold resistance, so measuring resistance with an ohmmeter will not give a meaningful resistance.

This is because the resistance of a light bulb has a positive temperature coefficient. Take a typical 60 W 120V light bulb, for instance... Its cold resistance is about 16 Ohms. Calculate current and power at 120 V and you get 7.5 A and 900 W. The truth is that at 60 W, the bulb pulls 0.5 A and has a resistance of 240 Ohms.

If you touch a power line with one hand, the current goes through your body. If you touch it with two hands, the current goes through your heart. They keep one hand in their pocket to prevent touching the line with both hands.

Power, P, is current, I, times voltage, E. (P = IE)

Not knowing one of voltage, E, or current, I, you can apply ohm's law ...

E = IR or I = E/R

... and come up with variations ...

P = I2R

P = E2/R

make sure you understood the text.

It doesn't.

In a series circuit, the largest voltage drop occurs across the largest resistor; the smallest voltage drop occurs across the smallest resistor.

R = resistance = rho * L / S

rho is resisitivity in [Ohm m], it depends on the material (Copper: 2e-8 [Ohm m])

L is wire length [m]

S is wire cross section [m]

EDIT: for high frequencies, you may also wanto to take sink effect into account (~MHz)

The working principle of a turbo generator is that of forcing extremely hot condensed air into the piston chamber. The hot condensed air reduces the need for fuel.

the value 'n' of meter constant indicates that consumption of energy is n KWh.

The input power, Pin, is reduced by different loss sources in the system. These reductions are the difference between input power & output power.

The losses are:

PSCL: Stator copper losses, or I2R losses

Pcore: Core losses

PRCL: Rotor copper losses

PF&W: Friction & windage losses

Pmisc: miscellaneous losses

All of these losses reduce the input power. The output power is the input power minus all of the losses.

Pout = Pin - PSCL - Pcore - PRCL - PF&W - Pmisc

Not Applicable

Many mutlimeters have this capability. You'll probably want a digital multimeter. If you do a good search, this should be easy to find. You'll need to read through the specifications carefully to make sure you find one that gives the level of accuracy you're looking for. the more accurate it is, the more you'll pay.

this always used in inverters and UPS As in standby UPS And line interactive UPS ,the output frequency must be always track the input frequency as it supply the load from utility in standby mode, for any change that will affect the load .

as example the frequency of the utility was with permitted values say 58Hz and suddenly the main power cutout, so UPS must be on same frequency so when convert to backup stored power mode ,the load doesn't affected and power continue to supply the load from the batterys through inverter , so output frequency must be always synchronized to utility frequency (mains) in case of any fault happened, hope i answered your question.

Sherif Salah

R & D Engineer at Arrow Electronics

Egypt

ohms law states V = I*R. If I is to remain the same, and R is increased, the voltage must also increase.

When a charged capacitor is connected to an uncharged capacitor charge flows from the charged to the uncharged capacitor until there is no net force on the charge carriers. This means that both capacitors are at the same potential, because if they were not, there would be an electric fieldand hence a force on the charge carriers of magnitudeand the charge carriers would move to equalize the potentials and reduce the electric field and hence the force, eventually to zero.

Of course, as charge flows from one capacitor to the other, the total charge is conserved.

In the diagram above, when switch is closed chraged flows from the top capacitor to the bottom. When charge has stopped flowing,

Also, because the potentials are equal(1)

Suppose then that the capacitor at top left is initially charged to potential ofand that it has capacitanceand is then connected to a capacitance

Initiallystores a charge

Then (3)

From (1) (4)

Sub (4) into (1) to get

Now usefor either capacitor to findUsing it for (2) gives

from A Level Physics Notes

The voltage rating of a fuse (in this case 125V or 230V) defines the maximum circuit voltage that the fuse is safe to be used on. A fuse with a voltage rating of 125V should not be used in a circuit with a voltage greater than 125V. If a 125V fuse were installed in a 230V circuit and an overload current occurred, the fuse could explode.

One way of using a flip flop as a frequency doubler is to create an oscillator at the desired doubled frequency, and then divide by two with the flip flop, resulting in the original frequency, and then controlling the oscillator with a phase locked loop.

Relay are operated by small current /voltage connected to Secondary side of Current Transformer and /or Voltage Transformer. The signal stimulates the magnetic substance nearby with the attracting force. This closes or opens the circuit being used in protection purpose.

A filter can be designed using an op amp by by replacing the resistors in an inverting or non-inverting amplifier with inductors or capacitors. Search for "op amp" on wikipedia for some simple schematics as a starting place. If you understand the basics of filter output and bode plot calculations, you should be able to replace R1 or R2 with C1 (1/jC1w) or L1 (jwL), and analyze the output vs. input characteristic.

Note op amps have limitations on frequency response, so this approach is good for fairly low frequencies - if you get into the high MHz, or GHz, a passive filter circuit becomes necessary.

Because if speed was used, the power system frequency would be changed. A synchronous generator spins at synchronous speeds.

Synchronous generators 101: A typical synchronous generator will have a field winding (typically on the rotor, or rotating part) and a stator winding (the stationary part where power is supplied to the power grid). Current is injected into the field winding, turning it into an electromagnet. This field current is controlled by the Automatic Voltage Regulator (AVR). The more current supplied to the field winding, the stronger the electromagnet becomes, and the more power is required from the prime mover (whatever is supplying the power - steam turbine, for example) to keep the generator spinning at synchronous speeds.

inductance

Typically the armature windings are in the stator of a generator, which does not rotate. Typically the field windings are on the rotor, which rotates.

what is surface type lamp holder

It depends on the rated voltage of the transformer winding -are you talking about a 12-V transformer winding or a 400-kV transformer winding? Obviously, there is no one answer to your question!