Electrical Formulas – Explaination,Formula and Solved

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Electrical Formulas
Electrical Formulas

Electrical Formulas

Volt – unit of electrical potential or motive force – potential is required to send one ampere of current through one ohm of resistance

Ohm – unit of resistance – one ohm is the resistance offered to the passage of one ampere when impelled by one volt

Ampere – units of current – one ampere is the current which one volt can send through a resistance of one ohm

Watt – unit of electrical energy or power – one watt is the product of one ampere and one volt – one ampere of current flowing under the force of one volt gives one watt of energy

Volt-ampere (VA) is a measurement of power in a direct current ( DC ) electrical circuit. The VA specification is also used in alternating current ( AC ) circuits, but it is less precise in this application, because it represents apparent power , which often differs from true power .

Kilovolt Ampere – one kilovolt ampere – KVA – is equal to 1000 volt amperes

Power Factor – ratio of watts to volt amperes

Most important Formulas:

Voltage V = I × R = P / I = √(P × R) in volts V         

Current I = V / R = P / V = √(P / R) in amperes A

Resistance R = V / I = P / I2 = V2 / P in ohms Ω    

Power P = V × I = R × I2 = V2 / R in watts W

 

Electrical Potential – Ohm’s Law

Ohm’s law can be expressed as:

V = R I      

V = P / I      

V = (P R)1/2       

Electric Current – Ohm’s Law

I = V / R        

I = P / V       

I = (P / R)1/2 

Electric Resistance – Ohm’s Law

R = V / I         

R = V2/ P       

R = P / I2   

Electric Power

P = V I         

P = R I2        

P = V2/ R

where

P = power (watts, W), V = voltage (volts, V)

I = current (amperes, A), R = resistance (ohms, Ω)

Electric Energy :Electric energy is power multiplied time, or

W = P t

where

W = energy (Ws, J), t = time (s)

Electrical Motors : Electrical Motor Efficiency

μ = 746 Php / Pinput_w 

where

μ = efficiency

Php = output horsepower (hp)

Pinput_w = input electrical power (watts)

or alternatively

μ = 746 Php / (1.732 V I PF)

Electrical Motor – Power

P3-phase = (V I PF 1.732) / 1,000 

where

P3-phase = electrical power 3-phase motor (kW)

PF = power factor electrical motor

Electrical Motor – Amps

I3-phase = (746 Php) / (1.732 V μ PF)  

where

I3-phase = electrical current 3-phase motor (amps)

PF = power factor electrical motor

Electrical measurements

Quantity

Name

Definition

frequency f

hertz (Hz)

1/s

force F

newton (N)

kg•m/s²

pressure p

pascal (Pa) = N/m²

kg/m•s²

energy E

work joule (J) = N•m

kg•m²/s²

power P

watt (W) = J/s

kg•m²/s³

electric charge Q

coulomb (C) = A•s

A•s

voltage V

volt (V)= W/A

kg•m²/A•s³

current I

ampere (A) = Q/s

A

capacitance C

farad (F) = C/V = A•s/V = s/Ω

A²•s4/kg•m²

 

READ HERE  Algebra Word Problems

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