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# How are amps related to wattage?

147148149 ###### 2010-05-05 16:26:29

An Amp (ampere) is a unit of measurement for electrical current flow. A Watt is a unit of measurement for electrical power. The relationship between current (Amps) and power (Watts) is generally not well understood.

The power (Watts) generated or transmitted by a system is directly proportional to the current (Amperes), and can be expressed in the following equation:

P = IV

Where:

· P is power in Watts

· I is current in Amperes

· V is voltage in Volts

The 'P=IV' equation is correct for all direct current (DC) circuits and for those alternating current (AC) circuits in which the power factor is 1.

When the current or the voltage is not constant, but varies with time t, the correct equation is:

p (t) = i (t) v (t)

Where:

· p (t) is the instantaneous real power in Watts

· i (t) is the instantaneous current in Amperes

· v (t) is the instantaneous voltage in Volts

P = I*V* pf

where

· P is average power in Watts

· I is RMS current in Amperes

· V is RMS voltage in Volts

· pf is the power factor of the load

When the current or the voltage is a perfect sine wave (which they rarely are),

pf = cosine (angle between the voltage and current)

so

P = I*V* cosine (angle between the voltage and current).

The power (Watts) consumed by a purely resistive system is directly proportional to the square of the current (Amperes), and can be expressed in the following equation:

P = I2R,

Where:

· P is power in Watts

· I is current in Amperes

· R is resistance in Ohms.

The power consumed can be much less than the power transmitted. For example, consider a power cable that carries 1,000 Amps at 100 Volts. The power delivered through the cable (P=IV) is 1,000 x 100, or 100,000 Watts. Let's assume the same power cable has a resistance of 0.001 Ohm (1 Milli Ohm) from one end to the other. The power consumed by that cable (P = I2R, which is the electrical power converted into heat) is 0.001 x 10002, or 1,000 Watts. That means there are only 99,000 Watts available after the current flows through the cable.

Now consider an identical power cable, but this time it carries 100 Amps at 1,000 Volts. The power delivered through the cable (P=IV) is 100 x 1000, or still 100,000 Watts. But this time the power consumed by that cable (P = I2R) is 0.001 x 1002, or 10 Watts. In this case, there are 99,990 Watts available after the smaller current flows though the same cable. This is why electrical power companies transmit high power at such high voltages - to reduce the amount of current flowing through the cables, and thus dramatically reducing the power lost to transmission.

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## Related Questions Amps are related to voltage in the following equation: Watts = Volts * Amps; so in order to answer your question, one would need to know the wattage. Wattage is volts times amps. To find amps when you know volts and watts, divide wattage by voltage. In this case, it would be 0.5 amps. There are zero watts related to 1.8 amps. Watts are the product of amps times volts. The equation that is used to find watts is Watts = Amps x Volts. Insert the circuit voltage into the equation and you will find the circuit's wattage load. In order to calculate the number of amps in 1000 volts, the wattage is required. The formula for calculating amps is: amps = watts / volts. Amps is a measure of current flowing in a circuit. Volt-Amps or (VA) is a measure of power and is equivalent to wattage for a pure resistive load. It is a measure of electrical power. It is Voltage multiplied by Amps. All electrical applicances should give it's wattage or at least it's voltage and Amps so you can work out the wattage. It should be noted that that figure is the maximum that appliance would use. It depends on the voltage. Multiply the Amps by the volts, and you get the wattage. So if you have 24 amps at 240V it draws 5760 watts. The amperage that a chandelier draws is based on the amount of bulbs and the wattage of the bulbs used in the fixture. Count the amount of bulbs and multiply that number by the wattage of the bulbs. Take this total wattage and use this formula. I = W/E. Amps = Watts/ Volts.

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