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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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?

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 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 $C$ ,

Question Image

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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

2.0 \times 10^{- 6} N

. Find out in each Fig.

(ii)

net force on

B

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 13

Two point-charges of

1.0 μC

and

- 0.25 μC

are placed in air at a distance of

0.40 m

from each other. Find out at which point on the line joining the two charges should a third charge be placed so that no force acts upon it?

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 14

Two point-charges

+ 9 e

and

+ e

are placed at a distance of

16 cm

from each other. At what point between these charges should a third charge

q

be placed so that it remains in equilibrium?

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 15

Three point-charges

q_{1,} q_{2,} q_{3}

, are in line at equal distances.

q_{2}

and

q_{3}

, are opposite in sign. Find the magnitude and sign of

q_{1}

, if the net force on

q_{3}

is zero.

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 16

ABC

is an equilateral triangle of side

10 m

and

D

is the mid-point of

BC

. Charges of

+ 100, - 100

and

+ 75 μ C

are placed at

B

C

and

D

, respectively. Find the force on a

+ 1 μ C

charge placed at

A

Important Questions on Electric Charges and Fields

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