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Physics Formulas

Electricity Formulas

Electricity is the flow of charge in a conductor from anode to cathode. Electricity has many applications in our day to day life. It is an essential tool that provides power to electrical devices at our homes and offices. Therefore, we can say that the flow of charge builds up the current which we are calling as Electricity. In this topic, we will discuss how the various Electricity Formulas are used in the theories of electricity. Relevant examples are also discussed here. Let us learn the interesting concept!

electricity formulas


Electricity Formulas

What is electricity?

Current and Electricity both are related concepts. As we know that all charges whether free or bound, are considered at the rest state. These charges during motion will constitute an electric current.

Such currents occur naturally in various many situations in the real world. Lightning is one such example of a phenomenon in which charges flow from the clouds to the earth through the atmosphere.

Electric current exists only due to the flow of charges. Both positive and negative charges may flow forward and backward. Conductors are a very good medium for electricity. Also, an electric charge will experience force if an electric field is applied. The current is the same for all cross-sections of a conductor of the non-uniform cross-section.

A very basic law regarding the flow of currents I Ohm’s Law. The concept of resistivity and conductivity both are interrelated and can be computed with the help of others.

Also, the power of electricity can be computed easily. The work is done per unit charge by the source while taking the charge from lower to higher potential is called the electromotive force, or emf, of the source.

Some Important Electricity Formulas are:

  1. Current formula

\(I = \frac {Q}{t}\)


I Current
Q Charge
t Time
  1. Voltage Formula

\(V =\frac {Q}{C}\)


V Voltage
Q Charge
C Capacitance


  1. Registance Formula

\(R = \frac {\rho \times l} {A}\)

R Registance
\(\rho\) Registivity
l Current
A Cross sectional Area


  1. Current Formula:

\(I= \frac {V}{R}\)

I Current
V Voltage
R Registance


  1. Electric Power Formula:

\(P = V \times I\)

P Electric Power
V Voltage
I Current


  1. Conductivity Formula:

\(\sigma = \frac{1}{\rho}\)

\sigma Conductivity
\rho Registivity

 Solved Examples

Q.1: Find out the amount of current flowing through the electric heater having a voltage of 220 V and resistance is \(100 \Omega.\)


As given in the problem:

Resistance R = \(100 \Omega\)

Voltage V = 220 V

The current formula is given as below:

\(I= \frac {V}{R} \)

\(I= \frac {220}{100} \)

I = 2.2 A

Therefore the amount of current flow is 2.2 A.

Q.2: An electrical lamp lights for 8 hours a day. It draws the current of 1 A. Find out the amount of charge flowing through the lamp.


Current, I = 1 A

Time taken, t = 8 hours

Time taken = \(8 \times 3600\)

Time taken = 28800 s,

Now, quantity of Charge,

\(Q = I \times t\)

\(Q = 1 \times 28800\)

Q = 28800 C

Therefore, amount of charge flowing will be 28800 C.

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