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 20

EASY

12th CBSE

IMPORTANT

Earn 100

Name and define the SI unit of charge.

Important Questions on Electric Charges and Field

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 21

In the relation

F, = k \frac{q_{1} q_{2}}{r^{2}}

, what is the value of k in free space?

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 22

Give the SI unit of electrical permittivity at free space

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 23

Write down the value of absolute permittivity of free space

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 24

Deduce the dimensional formula for the proportionality constant

k

in Coulomb's law.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 25

Write the dimensional formula for the permittivity constant

ε_{0}

of free space.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 26

What is the force of repulsion between two charges of

1 C

each, kept

1 m

apart in vacuum?

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IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Text Based Exercises>Q 27

Two point charges ' $q_{1}$ and ' $q_{2}$ ' are placed at a distance ' $d$ ' apart as shown in the figure. The electric field intensity is zero at a point $P$ on the line joining them as shown. Write two conclusions that you can draw from this.

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