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.

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 or V = W / Q E = Energy, W = Work done	Volts (V)
Resistance R	R = ρl / A ρ = Resistivity, l = length, A = Area or,  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.

Solution:

Given:

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.

Solution:

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