Two insulated charge copper spheres A and B have their centres separated by a distance of 50 cm . The charge on each of them is 6 . 5 × 10 - 7 C . What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved? (Take 1 4 π ∈ 0 = 9 × 10 9 )

Given, The initial charge, q = 6 . 5 × 10 - 7 C The initial distance, d = 50 cm = 0 . 5 m As the charge on each sphere is doubled, the charges on them respectively are, q A = q B = 2 × q = 2 × 6 .5 × 10 - 7 C = 1 .3 × 10 - 6 C Distance between the spheres is halved, so the new distance, r = d 2 = 0 .5 2 = 0 .25 m We know that the force is given by, F = q A q B 4 π ∈ 0 r 2 = 9 × 10 9 × 1.3 × 10 - 6 × 1.3 × 10 - 6 ( 0.25 ) 2 = 0.243 N

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An electric dipole with dipole moment $4 \times 10^{- 9} C m$ is aligned at $30^{°}$ with the direction of a uniform electric field of magnitude $5 \times 10^{4} N C^{- 1}$ . Calculate the magnitude of the torque acting on the dipole.

Important Questions on Electric Charges and Fields

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.11

A polythene piece rubbed with wool is found to have a negative charge of

3 \times 10^{- 7} C

. Estimate the number of electrons transferred. Is there a transfer of mass from wool to polythene? (The charge of the electron,

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

)

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.12

Two insulated charged copper spheres

A

and

B

have their centers separated by a distance of

50 cm

. What is the mutual force of electrostatic repulsion if the charge on each is

6.5 \times 10^{- 7} C

?
The radii of

A

and

B

are negligible compared to the distance of separation. (Take,

\frac{1}{4 {πε}_{0}} = 9 \times 10^{9}

)

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.12

Two insulated charge copper spheres $A$ and $B$ have their centres separated by a distance of $50 cm$ . The charge on each of them is $6.5 \times 10^{- 7} C$ . What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved? (Take $\frac{1}{4 π \in_{0}} = 9 \times 10^{9}$ )

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.13

Suppose there are two copper spheres

A

and

B

having identical sizes. The distance between the centers of sphere is

50 cm

and the charge on each sphere is

6.5 \times 10^{- 7} C

. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between

A

and

B

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.14

Figure shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge to mass ratio?

Question Image

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.15

Consider a uniform electric field

\vec{E} = 3 \times 10^{3} \hat{i} N / C .

What is the flux of this field through a square of

10 c m

on a side whose plane is parallel to the

y z

plane?

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.15

Consider a uniform electric field

E = 3 \times 10^{3} \hat{i} N / C .

What is the flux through the square of side

10 cm

if the normal to its plane makes a

60^{o}

angle with the x-axis?

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PHYSICS PART-1 TEXTBOOK FOR CLASS XII>Chapter 1 - Electric Charges and Fields>EXERCISES>Q 1.16

Consider a uniform electric field

E = 3 \times 10^{3} \hat{i} N / C

. What is the net flux of this uniform electric field through a cube of side

20 cm

oriented so that its faces are parallel to the coordinate planes?

An electric dipole with dipole moment 4 ×10-9 C m is aligned at 30° with the direction of a uniform electric field of magnitude 5×104 N C-1. Calculate the magnitude of the torque acting on the dipole.

Important Questions on Electric Charges and Fields

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An electric dipole with dipole moment $4 \times 10^{- 9} C m$ is aligned at $30^{°}$ with the direction of a uniform electric field of magnitude $5 \times 10^{4} N C^{- 1}$ . Calculate the magnitude of the torque acting on the dipole.