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 as 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 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

 Ohm (Ω)
 Resistance R  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

 Determine the current flowing through the electric heater have p.d of 220 V and resistance is 70 Ω.



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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