Question

 

Calculate what is the mass in kg of 1.00-C of electrons

Answer 1

To find mass in Kg of 1.00C of electrons.

Solution: We know that charge of an electron is negative and its value is - 1.602 x 10^-19 Coulomb

electron charge = - 1.602 x 10^-19 C

Now we need to find the number of electrons present in one Coulomb charge.

For that divide one coulomb charge by elctron charge.To find number of electrons no need to consider the negative sign i.e; discard negative sign.

Number of electrons present in one coulomb charge = 0ne coulomb / charge of electron

=1/( 1.602 x 10^-19 Coulomb)

   = 6.24219 x 10¹⁸  

   Therefore, one Coulomb charge contains 6.24219 x 10¹⁸ electrons.Hence if 1 Ampere current or when one Couloumb charge flows through a conductor, it implies that 6.24219 x 10¹⁸electrons are passed in 1 second.

Now to find the mass in Kg of 1.00 C electron ,we need to know the mass of one eletron.

  Mass of one electron = 9.1 x 10^-31 Kg

Thus, mass  in Kg of 1.00 C electron = mass of one electron x number of electrons in 1 C charge

= 9.1 x 10^-31 Kg x   6.24219 x 10¹⁸  

= 56.803 x 10^-31+18

= 56.803   x 10^-13

Mass  in Kg of 1.00 C electron = 5.6803 x 10^-12 Kg

In order to make the above calculation a bit clear.Consider the mass of an brick is 0.2 kg and there are 9 such bricks in a bag.Find the total mass of the bag?

To find total mass = masss of 1 brick x number of bricks

= 0.2 kg x 9 =1.8Kg

Similarly the above calculation was done.

Thus mass in Kg of 1.00 Couloumb of electrons is 5.6803 x 10^-12 Kg.

On rounding off the value mass in Kg of 1.00 Couloumb of electrons is 5.7 x 10^-12 Kg

.Hence if one Couloumb charge flows through a conductor, it implies that 6.24219 x 10¹⁸electrons are passed in 1 second whose mass will be equal to 5.7 x 10^-12 Kg.