Units to measure power

Answer 1

In the SI system the units of energy are Joules, and power is the rate of use or production of energy, so this is in Joules per second, another name for 1 Joule/sec is 1 Watt. Watts are used for power generally, not only for electricity, thus a car engine can be specified in watts or kilowatts. In the footpound system power is specified in horsepower, where 1 HP = 745.7 watts, but in scientific work the usual unit used is just watts.

Answer 2

Power : is the product of the voltage times the current in an electrical circuit measured in watts (P).

Voltage : is the electromotive force (pressure) applied to an electrical circuit measured in volts (E).

Current : is the flow of electrons in an electrical circuit measured in amperes (I).

Resistance : is the opposition to the flow of electrons in an electrical circuit measured in ohms (R).

Ohm's LawJust remember..."Twinkle, Twinkle, Little Star...I is equal to E over R"In its simplest form, Ohm's law states that the current in an electrical circuit is directly proportional to the applied voltage and the resistance of the circuit. The 3 most common mathematical expressions are:

E=I*R I=E/R R=E/I

Also, the power can be expressed as P=E*I and with a little algebra we can combined these expressions and derive P=E² / R

So what does all this mean? Well, for one thing it becomes clear that an appliance (load) that draws 1 amp (ampere) of current at 120 volts will draw 10 times as much current at 12 volts (1/10 the voltage) or 10 amps. Since P=E*I then 120 volts times 1 amp = 120 watts. Also, 12 volts times 10 amps = 120 watts. So you can see that the powerremains the same. As the Voltage goes down, the Amperage increases to maintain the power which will be determined by the 3rd factor, resistance.

Ok, now let's say you have a nice 1200 watthairdryer. Well, that would work out to 10 amps at 120 volts. But, when your power inverter uses the 12 volts supplied from your batteries, the amperage goes up to 100 amps to produce the same 1200 watts! (P=E*I). This means that even the very large cables connecting your batteries to the inverter will get warm. This is why it becomes impractical or impossible to run say, a 4000 watt electric clothes dryer. Even if you had large enough wires to handle the required 333 or so amps, your batteries would not last long.

It is true that the cables will not get as warm if the current can be reduced by increasing the voltage by using a 24 volt battery system or even a 48 volt battery system. This still will not change the amount of power that your batteries must supply.

The 12 basic formulas for Ohm's Law can be expressed as follows :

1. Voltage = the Square Root of Power * Resistance

2. Voltage = Power / Current

3. Voltage = Current * Resistance

4. Resistance = Voltage / Current

5. Resistance = Power / Current squared

6. Resistance = Voltage squared / Power

7. Current = Voltage / Resistance

8. Current = the Square Root of Power / Resistance

9. Current = Power / Voltage

10. Power = Voltage * Current

11. Power = the Current squared * Resistance

12. Power = the Voltage squared / Resistance

Answer 3

A power meter is used to measure power. Alternatively, a voltmeter and ammeter

can be used to measure the respective quantities, and then the power can be

calculated. Once the power is known, it can be expressed in any desired unit

suited to the application. A few choices are:

-- watt, microwatt, milliwatt, picowatt, kilowatt, nanowatt, megawatt, gigawatt

-- joule per second, newton-meter per second, calorie per day, kilowatt hour per month

-- dBm, dBw, dBk

Answer 4

WATT named after James Watt who worked on steam engines and improving their efficiency.

Answer 5

The ISO unit for power is the Watt.

Answer 6

the unit for power is watt

Answer 7

km/s2

Answer 8

Watt