A small brass sphere having a positive charge of 1 .7 × 10 − 8 C is made to touch another sphere of the same radius having a negative charge of 3 .0 × 10 − 9 C . Find the force between them when they are separated by a distance of 20 cm . What will be the force between them when they are immersed in an oil of dielectric constant 3 ?

When the charges are brought in contact charges on them becomes equal as the radii of the spheres are equal. Charge on each sphere q = 17 × 10 − 9 + − 3 .0 × 10 − 9 2 C = 7 × 10 − 9 C Separation r = 20 cm = 20 × 10 − 2 m Dielectric constant k = 3 From coulombs law, Force between them when they are placed in air F = 1 4 πε ∘ q 1 q 2 r 2 ⇒ F = 9 × 10 9 × 7 × 10 − 9 × 7 × 10 − 9 20 × 10 − 2 2 ⇒ F = 1 .1 × 10 − 5 N Force between the spheres when placed in air is 1 .1 × 10 − 5 N The force between them when they are placed in the oil of dielectric 3 is F = 1 4 πε ∘ k q 1 q 2 r 2 ⇒ F = 9 × 10 9 3 × 7 × 10 − 9 × 7 × 10 − 9 20 × 10 − 2 2 ⇒ F = 0 .37 × 10 − 5 N Force between the spheres when immersed in oil is 0 .37 × 10 − 5 N

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12th CBSE

IMPORTANT

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Obtain the dimensional formula of $ε_{\circ}$

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>Problems For Practice>Q 2

Calculate Coulomb force between two

α

- particles separated by a distance of

3.2 \times 10^{- 15} m

in air.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Problems For Practice>Q 3

Calculate the distance between two protons such that the electrical repulsive force between them is equal to the weight of either.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Problems For Practice>Q 4

How far apart should the two electrons be if the force each electron exerts on the other is equal to the weight of the electron? Given that

e = 1 .6 \times 10^{- 19} C

and

m_{e} = 9 .1 \times 10^{- 31} Kg

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Problems For Practice>Q 5

A pith-ball

A

of mass

9 \times 10^{- 5} kg

carries a charge of

5 μ C

. What must be the magnitude and sign of the charge on a pith-ball

B

held

2 cm

directly above the pith-ball

A

, such that the pith-ball

A

remains stationary?

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Problems For Practice>Q 6

Two identical metal spheres having equal and similar charges repel each other with a force of

103 N

when they are placed

10 cm

apart in a medium of dielectric constant 5. Determine the charge on each sphere.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Problems For Practice>Q 7

The distance between the electron and proton in hydrogen atom is $5 .3 \times 10^{- 11} m$ . Determine the magnitude of the ratio of electrostatic and gravitational force between them.

Given $m_{e} = 9 .1 \times 10^{- 31} kg$ , $m_{p} = 1 .67 \times 10^{- 27} kg$ , $e = 1 .6 \times 10^{- 19} C$ and $G = 6 .67 \times 10^{- 11} {Nm}^{2} {kg}^{- 2}$ .

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Problems For Practice>Q 8

Two identical metallic spheres, having unequal opposite charges are placed at a distance

0.90 m

apart in air. After bringing them in contact with each other, they are again placed at the same distance apart. Now the force of repulsion between them is

0.025 N

. Calculate the final charge on each of them.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 1 - Electric Charges and Field>Problems For Practice>Q 9

A small brass sphere having a positive charge of

1 .7 \times 10^{- 8} C

is made to touch another sphere of the same radius having a negative charge of

3 .0 \times 10^{- 9} C

. Find the force between them when they are separated by a distance of

20 cm

. What will be the force between them when they are immersed in an oil of dielectric constant

3

Obtain the dimensional formula of ε∘

Important Questions on Electric Charges and Field

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Obtain the dimensional formula of $ε_{\circ}$