SI unit of Current | What is the SI unit of Current
- Ampere
In physics when we deal with electricity, electric current signifies the strength of electricity. We know that current depends upon the amount free charges i.e electrons present in the conductor of given cross-section. Due to potential difference across terminals of conductor, charges flows inside the conductor and carries electricity.
Electric current is defined as amount of flow of electrons through given cross section of conductor in unit time. OR
The rate of flow of charge is also called as current.
If, ‘q’ be the charge flowing through the conductor in time ‘t’, then the electric current can be given as,
I = q/t
According to formula, SI unit of current can be coulomb/second.
Sir Andre Ampere, an experimental physicist had explained the relationship between electric current and magnetic field in his famous law known as Ampere’s law. Due to Ampere’s law it is convenient to find the magnitude of magnetic field produced due to long straight conducting wire, loop of wire, solenoidal coil, toroidal coil etc.
Considering his enormous work in the field of physics and mathematics, international system of units has renamed the name current in his honour as ‘ampere’
Then,
I = q/t
From the formula, SI unit of current should be,
I = coulomb/second
coulomb/second is then renamed as ampere
SI unit of current is then taken as ‘ampere’. Its symbol is ‘A’
(1 coulomb)/(1 second)=1 ampere
i.e. when one coulomb of charge flows through given cross section of conductor in one second, the current is said to equal to one ampere.
In many house hold appliances current flows in very small amount, so that the prefixes are used to indicate the current as,
1 mA= 10-3 A
1 µA = 10-6 A
1 nA = 10-9 A
Important Faq
Q.1) Why only metals can conduct electricity?
Answer: In last orbit of every metal, some loosely bounded electrons are always present (greater than 1, less than 4) which can be made available for conduction when electric energy is given by means of cell/battery. These electrons aren’t present in non metals so they are unable to carry electric energy.
Q.2) What is the number of electrons that can flow per second in 1 ampere of current?
Answer: We know that,
(1 coulomb)/(1 second)=1 ampere
Now, 1 coulomb charge=number of electrons ×charge on electron
1 coulomb charge=n ×charge on electron
∴ n= 1/ (1.67×10^-19)
∴ n= (1×10^19)/ 1.67
∴ n = 6.25 × 10^18