Two neutral insulating small spheres are rubbed against each other and are then kept 4 m apart. If they attract each other with a force of 3 . 6 N , then (i) calculate the charge on each sphere, and (ii) calculate the number of electrons transferred from one sphere to the other during rubbing.

(i) Given that two neutral insulating small spheres are rubbed against each other so they will have same magnitude of charge q 1 = q 2 = q and r = 4 m . As they attract each other with a force F = 3 . 6 N ⇒ F = 1 4 π ∈ ∘ q 1 q 2 r 2 = 9 × 10 9 × q × q 4 2 = 9 × 10 9 16 q 2 ⇒ q 2 = 3 . 6 × 16 9 × 10 9 = 64 × 10 - 10 ⇒ q = 64 × 10 - 10 1 2 = 8 × 10 - 5 C (ii) We know, total charge q = ne = n × 1 . 6 × 10 - 19 ⇒ 8 × 10 - 5 = n × 1 . 6 × 10 - 19 ⇒ n = 8 × 10 - 5 1 . 6 × 10 - 19 = 5 × 10 14

Two positively charged particles, each of mass 1 . 7 × 10 - 27 kg and carrying a charge of 1 . 6 × 10 - 19 C are placed at a distance d apart. If each experiences a repulsive force equal to its weight, find the value of d .

Let m A be the mass of the first particle and q A be the charge on it, m B be the mass of second particle and q B be the charge on it and d is distance of separation between both the particles. Given, m A = m B = 1 . 7 × 10 - 27 kg and q A = q B = 1 . 6 × 10 - 19 C Also, Given that both the particles experiences a repulsive force which is equal to its weight F = m A × g = m B × g = 1 . 7 × 10 - 27 × 9 . 8 N Using Coulomb's law, F = k q A q B d 2 ⇒ d 2 = k q A q B F ⇒ d 2 = 9 × 10 9 1 . 6 × 10 - 19 2 1 . 7 × 10 - 27 × 9 . 8 ⇒ d = 0 . 118 m

E M B I B E

Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 5

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Two identical particles each of mass $M$ and charge $Q$ are placed a certain distance apart. If they are in equilibrium under mutual gravitational and electric force then calculate the order of $\frac{Q}{M}$ in SI units.

Important Questions on Electrostatics

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 6

The force between two point charges is

100 N

in air. Calculate the force if the distance between them is increased by

\Rightarrow \frac{Q}{M} = 0.86 \times 10^{- 10} C {kg}^{- 1}

.

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 7

Two neutral insulating small spheres are rubbed against each other and are then kept $4 m$ apart. If they attract each other with a force of $\frac{Q}{M}$ , then

(i) calculate the charge on each sphere, and

(ii) calculate the number of electrons transferred from one sphere to the other during rubbing.

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 8

Two equal point charges

Q = + \sqrt{2} μ C

are placed at each of the two opposite corners of a square and equal point charges

q

at each of the other two corners. What must be the value of q so that the resultant force on

Q

is zero?

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 9

In the given figure three point charges are situated at the corners of an equilateral triangle of side $10 cm$ . Calculate the resultant force on the charge at $B$ . What is its direction?

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 10

Two positively charged particles, each of mass

1.7 \times 10^{- 27} kg

and carrying a charge of

1.6 \times 10^{- 19} C

are placed at a distance

d

apart. If each experiences a repulsive force equal to its weight, find the value of

d

.

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IMPORTANT

Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 3>Q 1

$A B C$ is a right angled triangle. Calculate the magnitude of force on charge - $Q$ .

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 3>Q 2

Charge $Q$ of mass $m$ revolves around a point charge $q$ due to electrostatic attraction. Show that its period of revolution is given by $T^{2} = \frac{16 π^{3} ε_{0} m R^{3}}{Q q}$ .