Question

In discharge tube $ 3\times {{10}^{16}} $ number of electrons moves towards left and $ 2\times {{10}^{16}} $ Protons move towards right per second, the current across the cross section is:
(a) $ 80amp. $ towards right
(b) $ 80amp. $ towards left
(c) $ 80mA. $ towards right
(d) $ 80mA. $ towards left

Answer 1

Hint :Both the charges are moving opposite to each other thus the current to each carrier will add up. In ordinary matter negative charge is carried by electrons and positive charge by protons.
Formula used:
 $ I=nq $
Where,
 $ n $ is no. of charges and $ q $ is unit of charge i.e. $ 1.6\times {{10}^{-19}} $

Complete Step By Step Answer:
Given data: $ {{n}_{e}}\to $ no. of electrons $ =3\times {{10}^{16}} $
 $ {{n}_{p}}\to $ no. of protons $ =2\times {{10}^{16}} $
Current will add up as charges are moving opposite.
 $ \therefore I={{n}_{e}}q+{{n}_{p}}q $
 $ I=3\times {{10}^{16}}+1.6\times {{10}^{-19}}+2\times {{10}^{16}}\times 1.6\times {{10}^{-19}} $
 $ I=\left( 3\times {{10}^{16}}+2\times {{10}^{16}} \right)1.6\times {{10}^{-19}} $
 $ I=5\times {{10}^{16}}\times 1.6\times {{10}^{-19}} $
 $ =8\times {{10}^{-3}}amp. $
 $ \therefore I=8mA $
Electrons flow from negative to positive and current from positive to negative.
$ \therefore $ The correct option is (d) $ 80mA $ towards left.

Additional Information:
Electric charge is a conserved property. The net charge of an isolated system, the amount of positive charge minus the amount of positive charge minus the amount of negative charge, cannot charge. Electric charge produces electric fields. A moving charge also produces a negative field. The interaction of electric charges with an electromagnetic or Lorentz force which is one of the main fundamental sources of physics. Michel Faraday was the first to note the discrete nature of electric charge in his experiment of electrolysis. By convention, the charge of an electron in negative and proton is positive, charges with the same sign repel and opposite sign attract each other. The electric charge of a microscopic object is the sum of electric charges of the particles that make it up. This charge is small because it is made up of atoms which have equal protons and electrons. Which yields no charge as zero making the atom neutral.

Note :
When the net electric charge of an object is non-zero and motionless, the phenomenon is known as static electricity. This can easily be produced by rubbing two dissimilar materials together. In this way non-conductive materials can be charged to a significant degree.
When an object's net charge is zero, the charge can be distributed non-uniformly in the object. In such cases the object is said to be polarized. The charge due to polarization is known as bound charge. Coulomb’s law quantifies the electrostatic force between two particles by asserting that the force is proportional to product of their charges and inversely proportional to the square of distance between them.