Electric Current and Potential
Electric current
Electric current is responsible for all the electrical appliance working in our home. When the switch is off all the appliances stop working because no current flows in the circuit. All the modern devices such as mobile, camera, TV, AC, refrigerator, satellites in space use electric current.
What is electric current?
All the metals have large number of free electrons which are in random motion. The charge carried by one electron is 1.6 x 10^-19C. When a battery or cell is connected across the wire the free electrons start moving in one direction this setups electric current in the circuit. We can say the electric current is the flow of charges in a wire or circuit.
Electric current is defined as "the flow of charges per unit area in a conductor or metal.
The direction of the flow of current (also called as conventional current ) is opposite to the direction of the flow of electrons. Current flows form positive to negative terminal and electrons flow from negative to positive terminal. No, its not wrong. Because when the concept of current was explained, electrons were not discovered. So for the convention, the flow of current was taken from a positive terminal to negative terminal.
What is the formula of current:
Consider charge 'q' flows through a cross-section in time t. The current can be written as
I = q/t
Total charge (q) flowing through the cross section is equal to the number of electron (n) and charge on one electron (e)
q= n e
I = ne /t
The unit of current is ampere(A).
Also, the unit of current is coulomb/ second(c/s).
1 A= 1C/ 1s
How to define Ampere?
One ampere defined as, "one ampere (A) of current is equal to one coulomb (C) of charge flowing in one second(s)".
Electric potential.
The motion of charges in the circuit is random. But unit direction flow requires work form the battery. The battery has to do work to push the charges from one end to another end. While doing so, the battery loses its charge and energy.
Electric potential is a very important quantity which explains how much work is done in pushing per unit of charge.
It is defined as the work done per unit charge.
It is denoted by a letter 'v' and its unit is volt after the name of scientist Alessandro Volta.
Electric potential difference:
It is defined as the work done per unit charge between any two points in the circuit.
the unit of electric potential is also Volt.
v = w/q
What is Ohm's law?
This law is named after the German scientist George Simon Ohm.
According to the ohms law, the electric current flowing through a metallic wire is directly proportional to the potential difference across it when the external condition is kept constant; for example temperature and type of resistor.
When we plot a graph of voltage and current it gives us a straight line. The materials which give a straight line graph are called Ohmic material, whereas the materials which give other types of graph are called non-ohmic material.