A stationary oil drop between two parallel plates has a charge of 3 . 2 × 10 - 19 C and a weight of 1 . 6 × 10 - 14 N . Find the electric field acting on the drop.

Given, Charge q= 3 . 2 × 10 - 19 C , Weight of the oil drop = w = mg = 1 . 6 × 10 - 14 N According to question Let stationary oil drop is between plate A and B So, that force on oil are equal in magnitude and opposite in direction i.e.,qE=mg ⇒ E = mg q = 1 · 6 × 10 - 14 3 · 2 × 10 - 19 NC - 1 = 0 . 5 × 10 5 NC - 1 = 5 . 0 × 10 4 NC - 1

Two point-charges of + 1 μC and - 1 μC are kept at a distance of 2 cm . They form an electric dipole. This dipole is situated in a uniform electric; field of 1 × 10 5 NC - 1 , with dipole moment vector p making an angle of 30 ∘ with the field. Calculate (i) the magnitude of electric dipole moment.

Given, q 1 = + 1 × 10 - 6 C q 2 = - 1 × 10 - 6 C Dipole length = 2 l = 2 cm = 2 × 10 - 2 m Electric field intensity = E = 1 × 10 5 NC - 1 Dipole moment makes angle 30 ° i . e . , θ = 30 ° Electric dipole moment = p = 2 l · q = 2 × 10 - 2 × 1 × 10 - 6 = 2 × 10 - 8 Cm

Two point-charges of + 1 μC and - 1 μC are kept at a distance of 2 cm . They form an electric dipole. This dipole is situated in a uniform electric field of 1 × 10 5 NC - 1 , with dipole moment vector p making an angle of 30 ∘ with the field. Calculate, (ii) the torque acting on the dipole.

Given, q 1 = + 1 × 10 - 6 C q 2 = - 1 × 10 - 6 C Dipole length = 2 l = 2 cm = 2 × 10 - 2 m Electric field intensity = E = 1 × 10 5 NC - 1 Dipole moment makes angle 30 ° i . e . , θ = 30 ° Torque on dipole = t = PE sin θ = 2 × 10 - 8 × 1 × 10 5 × sin 30 ° = 2 × 10 - 3 × 1 2 = 1 × 10 - 3 Nm

Two point-charges of + 1 μC and - 1 μC are kept at a distance of 2 cm . They form an electric dipole. This dipole is situated in a uniform electric; field of 1 × 10 5 NC - 1 , with dipole moment vector p making an angle of 30 ∘ with the field. Calculate (iii) When would be the torque maximum? How much?

Given, q 1 = + 1 × 10 - 6 C q 2 = - 1 × 10 - 6 C Dipole length = 2 l = 2 cm = 2 × 10 - 2 m Electric field intensity = E = 1 × 10 5 NC - 1 Dipole moment makes angle 30 ° i . e . , θ = 30 ° For t → t m a x m , sinθ = m a x m = 1 = sin 90 ° ⇒ θ = 90 ° ∴ t m a x m = PEsin 90 ° = 2 × 10 - 8 × 1 × 10 5 = 2 × 10 - 3 Nm It is maximum when it is perpendicular to electric field.

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Electric charges $\pm 1000 μC$ are placed at points $A$ and $B$ , respectively at a distance of $2 m$ from each other. Calculate the electric fields at $(i)$ mid-point of the line $AB$ .

Important Questions on Electric Charges and Fields

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IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 24

Electric charges

\pm 1000 μC

are placed at points A and B, respectively at a distance of

2 m

from each other. Calculate the electric field at a point at equal distance of

4 m

from each charge.

MEDIUM

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 25

A stationary oil drop between two parallel plates has a charge of

3.2 \times 10^{- 19} C

and a weight of

1.6 \times 10^{- 14} N

. Find the electric field acting on the drop.

MEDIUM

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 26

Two charges, one

+ 5 μC

and other

- 5 μC

are placed

1 mm

apart. Calculate the dipole moment.

MEDIUM

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 27

A system has two charges

q_{A} = + 0.25 μC

and

q_{B} = - 0.25 μC

at points

A (0, 0, - 15 cm)

and

B (0, 0, + 15 cm)

, respectively. Find the total charge and electric dipole moment of the system.

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IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 28

Two charges of

+ 2.4 μC

and

- 2.4 μC

are at a distance

2.5 \times 10^{- 3} m

apart from each other. Determine the magnitude of the electric field in the broad-side-on position at a distance of

0.30 m

from this dipole. If the dipole be rotated through

90^{\circ}

, then what will be the intensity of the field?

MEDIUM

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 29

Two point-charges of

+ 1 μC

and

- 1 μC

are kept at a distance of

2 cm

. They form an electric dipole. This dipole is situated in a uniform electric; field of

1 \times 10^{5} {NC}^{- 1}

, with dipole moment vector p making an angle of

30^{\circ}

with the field. Calculate (i) the magnitude of electric dipole moment.

MEDIUM

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 29

Two point-charges of

+ 1 μC

and

- 1 μC

are kept at a distance of

2 cm

. They form an electric dipole. This dipole is situated in a uniform electric field of

1 \times 10^{5} {NC}^{- 1}

, with dipole moment vector p making an angle of

30^{\circ}

with the field. Calculate, (ii) the torque acting on the dipole.

MEDIUM

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 1 - Electric Charges and Fields>QUESTIONS>Q 29

Two point-charges of

+ 1 μC

and

- 1 μC

are kept at a distance of

2 cm

. They form an electric dipole. This dipole is situated in a uniform electric; field of

1 \times 10^{5} {NC}^{- 1}

, with dipole moment vector p making an angle of

30^{\circ}

with the field. Calculate (iii) When would be the torque maximum? How much?

Electric charges ±1000 μC are placed at points A and B, respectively at a distance of 2 m from each other. Calculate the electric fields at (i) mid-point of the line AB.

Important Questions on Electric Charges and Fields

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Electric charges $\pm 1000 μC$ are placed at points $A$ and $B$ , respectively at a distance of $2 m$ from each other. Calculate the electric fields at $(i)$ mid-point of the line $AB$ .