A glass rod, when rubbed with silk cloth, acquires a charge of 1 .6 × 10 − 13 C . What is the charge on silk cloth?

An atom consists of negatively charged electrons revolving around positively charged nuclei. The negative charge appears in the form of electrons and positive charge appears as protons inside the nucleus. Upon supplying very little amount of energy electrons can leave an atom, making it ionized (or positively charged). As the electron leaves the atom there is an excess of positive charge on the atom now. In our case this is what happens with the atoms in the glass rod. Some of the electrons from the glass rod got transferred from the rod to the silk cloth when they were rubbed against each other. The conservation of charge says that charge can neither be created nor be destroyed. So, only a transfer of charge could occur. Therefore, when the glass rod acquired a positive charge of 1 . 6 × 10 − 11 C , the silk cloth must acquire a charge of − 1 . 6 × 10 − 11 C .

In the relation F , = k q 1 q 2 r 2 , what is the value of k in free space?

We know coulomb’s law gives the expression for magnitude of electrostatic force between two charges at some distance as, F = 1 4 πε ∘ × q 1 q 2 r 2 Where, q 1 and q 2 are the two charges. r is the distance between two charges. ε ∘ is a permittivity of vacuum. Permittivity of vacuum ε ∘ is the ability of vacuum to permit electric field lines. It is always constant. ε ∘ has a value of, ε ∘ = 8 . 854 × 10 − 12 Fm - 1 Therefore, From Coulomb’s law we know that the value of k is k = 1 4 πε ∘ Here, π is taken as π = 3 . 14 . Substituting the values, we get k = 1 4 × 3 . 14 × 8 . 85 × 10 - 12 = 8 . 99 × 10 9 ≈ 9 × 10 9 Nm 2 C - 2 So, the value of constant k is coulomb’s equation is found as k = 9 × 10 9 Nm 2 C - 2

E M B I B E

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 14

EASY

12th CBSE

IMPORTANT

Earn 100

Is the total charge of the universe conserved?

Important Questions on Electric Charges and Field

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 15

A glass rod, when rubbed with silk cloth, acquires a charge of

1 .6 \times 10^{- 13} C

. What is the charge on silk cloth?

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 16

Two insulated charged copper spheres

A

and

B

of identical size have the charges

q_{A}

and

q_{B}

respectively. A third sphere

C

of the same size but uncharged is brought in contact with the first and then with the second and finally removed from both. What are the new charges on