Voltage, Current, and Power Interview Questions 

From the Primary, I have a 15KVA transformer, then my electric meter, then a 900 meters service drop wire (private line), (#2 aluminum, twisting / one with no insulation. About 1 cm diameter each (I think it's called line to ground)). At my area the voltage from the socket reads 240V, but when I plug my 3HP motor submersible pump, the voltage reading drops to 165V.

1.A 100W lamp is connected to a 250V power pack.There is a resistor connected in parallel to the lamp,with a 14A current flowing through it . An ammeter in series with the lamp reads 7A.
a)What is the current through the power pack?
b)What is the voltage through the lamp?
c)What is the voltage through the resistor?
d)Calculate the power of the lamp

2.Three identical lamps,in series, are connected to a 4V power supply. One of the lamps has a fourth identical lamp connected in parallel. One of the lamps in parallel has a voltage of 1V.
a)What is the voltage of the second lamp in parallel?
b)What is the voltage across each of the remaining lamps?
c)If the current through the power supply is12A ,what is the current throgh each of the lamps in parallel?

3.Three resistors are connected in parallel. The power supply is 14V.
a)What is the voltage across the second resistor?
b)If there is 14A through the power supply,2Athrough the first resistor and 5A through the second resisto

When you are selecting a motor the first thing to consider is torque. That will tell you what it takes to actually get the load started and turn it at all.

Close behind that is speed. You need to know how fast you want the load to turn. AC motors have only a few standard speed ratings. The synchronous speeds are given by RPM(revolutions per minute)=120*frequency/poles. The frequency is usually 50 or 60 Hz. The number of poles is an even number, usually 2, 4 or 6. Motors with more than 6 poles are rarely used. You will probably need some kind of speed reduction such as a gear box or pulleys.

Power is proportional to speed X torque. Horsepower = LbsFt X RPM / 5252. Watts = Nm X Revs per sec.

After that you decide what voltage to use. The power and voltage determine the current. If the current is too high for practical wiring, you are forced to use a higher voltage.

How do i calculate power/voltage/current using the following equation? for both problems and please explain. thx.
I=V/R

how much current does a W bulb require in a 110 V circuit?

what is the resistance of a light bulb connected to a 110 V outlet that requires a current of 0.2 A?

what is the voltage and the current if the power is 5000 watts and the resistance is 50 ohms?

The measured average power, current, and voltage in a circuit are 880 W, 5 Arms and 220 Vrms , respectively. Determine the following. Phase angle ? =? power factor cos ? =? and apparent power Papp = ?

What is the meaning of
Rated speed
Rated power
Current at rated speed
Voltage at rated power
in the specification of a wind turbine alternator?

does it mean the battery only charged at those specific power/speed/voltage?

any difference with just "speed/power/current/voltage" alone?

here is an example,
http://www.alxion.com/e_produit/82.pdf

thanks

One sentence will do. Please, please don't just type it into google, and copy and paste an answer. I can do that myself. I just need someone who understands it to just type in an answer!!!

i keep seeing questions asking to find the power dissipated, power delivered, how much power is extracted; in current or voltage sources. I know resistors will always have + power but like how do u know the v in vi is negative or positive? is it like dissipated = positive or negative answer, delivered = + or - & delivered = + or -, or does it vary?

In a lay man's language, increasing system load under steady excitation will reduce your voltage, increase current, reduce your power factor and frequency.The opposite also holds.

Describe the relationships between voltage, current, impedance and power in the primary and secondary windings of a transformer?

We are planning to construct a voltage regulated power supply as our project but our teacher told us that it would be better to construct a current and voltage regulated power supply instead.We are just wondering what difference can a current regulated power supply do.

An Amplifier has an input resistance of 20 Ohms, an output resistance of 10 Ohms, and a short-circuit current gain of 3000. The signal source has an internal voltage of 100mV rms and an internal impedance of 200 Ohms. The amplifier load is a 5-Ohm resistance. Find the current gain, voltage gain, and power gain of the amplifier. If the power supply has a voltage of 12V and supplies an average current of 2A, find the power dissipated in the amplifier.

voltage is a potential difference between two points, usually in a circuit. you can think of it as analogous to gravity potential...though don't carry that analogy too far or else you get yourself into trouble with energy. electrons/other charged particles will tend to flow from high potential places to low.

current is the amount of charge passing through a surface in a given time; it is usually denoted by dQ/dt.

power, when defined mechanically, is a measure of energy per unit time. your light bulbs are measured in units of power (watts). with electrical circuits, power = IV, which is current times voltage (for relatively simple circuits).

energy is probably the most abstract concept of these. it is...a measure of the ability to do work, to put it sort of vaguely. energy equations in circuits vary depending on your components.