AC FundamentalsAlternating CurrentBasic / Important Electrical FormulasBasic Electrical FundamentalsDC Circuits

# Power Formulas in DC, AC Single Phase & Three Phase Circuits.

**Power Formulas in DC, AC Single Phase and AC Three Phase Circuits**

Back to basic, below are the simple Power formulas for Single Phase AC Circuit, Three Phase AC Circuits and DC Circuits. You can easily find electric **power in watts** by using the following **power formulas in electric circuits**.

**Power Formulas in DC Circuits**

- P = V x I
- P = I
^{2}x R - P = V
^{2}/ R

Where:

**P** = **Power** in **Watts**

**V** = **Voltage** in **Volts**

**I** = **Current** in **Amperes**

*R = Resistance in Ohms (Ω)*

**Power Formulas in Single Phase AC Circuits**

- P = V x I x Cos Ф
- P = I
^{2}x R x Cos Ф - P = V
^{2}/ R (Cos Ф)

Where:

**P** = **Power** in **Watts**

**V** = **Voltage** in **Volts**

**I** = **Current** in **Amperes**

*R = Resistance in Ohms (Ω)*

**Power Formulas in Three Phase AC Circuits**

- P = √3 x V
_{L }x I_{L}x Cos Ф - P = 3 x V
_{Ph }x I_{Ph}x Cos Ф - P = 3 x I
^{2}x R x Cos Ф - P = 3 (V
^{2}/ R) x Cos Ф

Where:

**P** = **Power** in **Watts**

**V** = **Voltage** in **Volts**

**I** = **Current** in **Amperes**

*R = Resistance in Ohms (Ω)*

**Cos Ф** = **Power Factor**

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You may also read:

- Basic Electrical Quantities Formulas With Simple Explanation (in DC Circuits.)
- Electrical Formulas AC & DC Circuits (Single-φ & 3-φ)
- P, V, I, R, Formulas.( Very Simple)
- Power, Voltage, Current, Resistance Formulas For DC Circuits ( With Easy Explanation)
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- Motor H.P, input Voltages, Full load Current, Breaker Size, And Copper Wire Size Formulas (Single Phase & 3-Phase Motors)

sir i want to know in detail about KVA

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can you tell me about load calculation and size of wire depending on load

Check this…<br />https://www.electricaltechnology.org/2013/10/How-to-determine-the-suitable-size-of-cable-for-Electrical-Wiring-Installation-with-Solved-Examples-in-both-British-and-SI-System.html

Check the explanatory answer here:<br />https://www.electricaltechnology.org/2013/04/normal-0-false-false-false-en-us-x-none.html

Dear sir,

i want to know about contactor relays its types rating wiring could you please help me in this matter.

sir i want to know about single phase circuit. pls help me.

dear i want to know about, why we rated prim-mover in MW (Mega-Watt) while our Generator rated in KVA………please tell me>.

this Answer KVA*.8=KW And KW/1000= Mega Watt

The out put of the Generator will change depending on the load power factor ,0.8, 0.9 or unity power factor which is only in lighting load also if capacitance load is their the KW OR MEGA WATT WILL BE MORE.

In 45 kw ac drive, output motor consumes 30kw, then another how much dc current use in dc bus.

Means what is the formula od dc current.

Please help….

Formula P=(I^2)*(R)*Cos(A) is wrong. Currect answer is P=(I^2)*R.

P=3*(I^2)*(R)*Cos(A) is wrong. Currect answer is P=3*(I^2)*R.