Two similarly and equally charged identical metal spheres A and B repel each other with a force of 2 . 0 × 10 - 5 N . A third identical, uncharged sphere C is touched with A and then placed at the mid-point between A and B . What is net electric force on C ?

In first condition, q 1 = q 2 = q Force of repulsion = F = 2 . 0 × 10 - 5 N F = 1 4 π ϵ 0 · q 2 r 2 = 9 × 10 9 q 2 r 2 q 2 r 2 = 2 × 10 - 5 9 × 10 9 = 2 9 × 10 - 14 When uncharged sphere C touched with A , then charge on A and C = q + 0 2 = q 2 Now C , is placed at middle of A and B F net at sphere C = F eA - F eB = 1 4 π ε 0 . q 2 · q 2 ( r / 2 ) 2 - 1 4 π ϵ 0 · q · q / 2 ( r / 2 ) 2 = 1 4 π ϵ 0 · q 2 × 4 4 r 2 - 1 4 π ϵ 0 · q 2 × 4 2 r 2 = 1 4 π ε 0 · q 2 r 2 [ 1 - 2 ] = - 1 4 π ε 0 · q 2 r 2 = - 2 . 0 × 10 - 5 N Magnitude of net force = 2 . 0 × 10 - 5 N - ve sign indicates that direction will be opposite to B mean towards A

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The mutual electrostatic force of attraction between two small spheres carrying charges $+ 0.4 μC$ and $- 0.8 μC$ in air is $0.2 N$ . What is the separation between the two spheres?

Important Questions on Electric Charges and Fields

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 5

How far apart the two electrons be, if the force between them equals the weight of an electron? What in case of protons?

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 6

Two positive charges distant

0.1 m

apart, repel each other with a force of

18 N

. If the sum of the charges be

9

micro-coulomb

(μC)

, then calculate their separate values.

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 7

The distance between two negatively-charged dust particles is $1 mm$ and they repel each other with a force of $4.0 \times 10^{- 5} N$ . If the charge on one particle is $4$ times that of the other, then find out the number of electrons charging them separately. The charge on electron is $(5 / 3) \times 10^{- 19} C$ .

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 8

Two point-charges of

+ 2 μC

and

+ 6 μC

, repel each other with a force of

12 N

. If each is given an additional charge of

- 4 μC

, then what will be the new force?

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 9

Two identical metallic balls

A

and

B

have charges

+ 40

and

- 10 μC

respectively. The distance between them is

2.0 m

. What is the magnitude and type of force acting between them? They are touched to each other and again separated by a distance of

2.0 m

from each other. Calculate the new force between them. What will be the force if one ball is connected to earth?

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 10

Two similarly and equally charged identical metal spheres

A

and

B

repel each other with a force of

2.0 \times 10^{- 5} N

. A third identical, uncharged sphere

C

is touched with

A

and then placed at the mid-point between

A

and

B

. What is net electric force on

C

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 11

Two conducting spheres

A

and

B

of the same size are situated at some distance apart. Each has a charge of

+ q

Coulomb and they repel each other with a force of

10^{- 5} N

. A third conducting uncharged sphere

C

of same size is first touched with $A$ and then with $B$ and then placed exactly between

A

and

B

. Calculate the resultant force on

C

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 12

In the adjoining figures are shown three particles $A$ , $B$ and $C$ which are equally charged. The force acting on $B$ due to $A$ is $2.0 \times 10^{- 6} N$ . Find out in each Fig. $(i)$ force exerted on $B$ by $C$ ,

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The mutual electrostatic force of attraction between two small spheres carrying charges +0.4 μC and -0.8 μC in air is 0.2 N. What is the separation between the two spheres?

Important Questions on Electric Charges and Fields

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The mutual electrostatic force of attraction between two small spheres carrying charges $+ 0.4 μC$ and $- 0.8 μC$ in air is $0.2 N$ . What is the separation between the two spheres?