Electricity Formulas

Electricity is the flow of charge in a conductor from anode to cathode. Electricity has varied applications. It acts as a tool to provide power to electrical devices. We can say the flow of charge builds up the current, which we call Electricity. To understand how the Electricity is generated, we need to understand the various basic parameters related to it like the voltage, current, resistance, conductivity and the relation among them.

Electricity Formula Diagram

Some of the commonly used Electricity formulae are listed below.

Quantity Formulas Unit
 Current I  I = Q / t

Q = Charge

t = time taken

 Amperes (A)
 Voltage V V = E / Q


V = W / Q

E = Energy, W = Work done

 Volts (V)
 Resistance R  R = ρl / A

ρ = Resistivity,

l = length,

A = Area


 R = V / I

 Ohm (Ω)
 Power P  P = VI  Watts (W)
 Conductivity σ  sigma = 1 / ρ  Siemens per meter (S/m)


Electricity Formulas are applied in calculating the unknown electrical parameters from the known in electric circuits.

Solved Examples

Example 1

An electric heater has a potential difference of 220 V and resistance is 70 Ω. Determine the magnitude of the current flowing through it.



Resistance R = 70 Ω

Voltage V = 220 V

The current formula is given by

I = V / R

= 220 / 70

I = 3.1428 A

Example 2

An electrical lamp lights for 4 hours and draws a current of 0.5 A. Calculate the amount of charge flowing through the lamp.


Current I = 0.5 A

Time taken t = 4 hours

t= 4 × 3600 = 14400 s,

Charge Q = I × t

= 0.5 ×14400

Q= 7200 C



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  16. Your electricity formula diagram was very helpful in that it brought back many of the formulas that I have forgotten in my aging years. It is nice to have an easy reference to go to. However, I ask that you review your formula in the upper right hand quadrant where you have V = V/I. Unless I have mistaken the intent, I believe that this should be V = W/I.

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