• When a negatively charged body is grounded electrons from the body flow to the earth and the body becomes neutral.
• On the other hand, when a positively charged body is grounded electrons coming from the earth neutralize the body.

Additional Information: Earth is an electric conductor. Earthing is defined as “the process in which the instantaneous discharge of the electrical energy takes place by transferring charges directly to the earth through low resistance wire.” When a charged body is connected to the earth, it becomes electrically neutral. 

• Ions are formed when atoms gain or lose electrons.
• Gaining electrons changes an atom into a negative ion.
• Losing electrons changes an atom into a positive ion.

Therefore, the correct answer is C. 

• On rubbing a rubber rod with wool, the electrons from the wool get transferred to the rubber rod.
• The wool now has a deficiency of electrons and so is positively charged.
• On the other hand, the rubber rod has an excess of electrons and hence is negatively charged.
• In the above example, the wool undergoes positive electrification.
• It is to be noted that it is the electrons and not the protons that get transferred during positive (and negative) electrification.
• Here, the transfer of electrons and mass transfer respectively takes place from wool to the rubber rod.

Here, n = 30 
e = -1.6 x 10^-19 C
We know that q = n ∗ e

Therefore, q = 30 * (1.6 x 10^-19 C)
q = - 4.8 ∗ 10^-18 C

• He atom has 2 electrons.
• So, 1 mole of He has 2*N(N is Avogadro's no.) electrons.
• Then total -ve charge in 1 mole He gas is =  2 * N * charge of 1 electron
  = 2 * (6.022 * 10²³) * (1.6 * 10^-19) = 1.92 * 10⁵ C 

• Physical quantity whose S.I. unit is JC^-1 is Electric potential.
• It is a Scalar quantity.

Additional Information:

• The SI base unit of electric flux is voltmeters (V m) which is also equal to newton-meters squared per coulomb (N m² C^-1). Also, electric flux is a scalar quantity. 
• Electric potential is expressed in units of joules per coulomb (i.e., volts). It is also a scalar quantity. 

According to Quantisation of Charge we know that,
Q = ne
Therefore, 1 coulomb of Charge = n * 1.6 * 10^-19 
⇒ 1/ 1.6 × 10^-19 = n
⇒ n = 6.25 × 10¹⁸

If we have two bodies with charge q₁ and q₂ on them and we are given q₁ + q₂ = 0. It means the net charge on the system is zero.

This is possible only if q₁ and q₂ are equal and opposite.

That is, q₁ = +q and q₂ = -q or vice versa. 

Such that, q₁ + q₂ = +q + (-q) = 0

During rubbing, glass rod acquires + ve charges and silk cloth acquires - ve charges.
The glass rod will have postive charge equal in value to the negative charge lost by the silk.
∴ the charge on the glass rod is + 1.6×10^{- 19}C

Additional Information: When a glass rod is rubbed with silk, glass happens to lose electrons easily and silk grabs them away from the glass atoms. So after rubbing, the glass becomes positively charged and the silk becomes negatively charged. Thus equal but opposite charges are produced on both. 

• A body consists of atoms that have electrons, protons and neutrons. The electrons have a negative charge. The protons are positively charged and the neutrons are neutral.
• The atom is neutral because the positive and negative charges cancel out each other.
• On removing electrons, an excess of protons are present and thus the body is said to be positively charged.