A polythene piece rubbed with wool is found to have a negative charge of 3 . 2 × 10 - 7 C . Find the> (a) number of electrons transferred. (b) mass gained by the polythene.

Given, Net charge on polythene, Q = 3 . 2 × 10 - 7 C (a) According to Quantization of electric charge, Net charge on polythene is integral multiple of basic charge ⇒ Q = n e where n is number of electron transferred and e is charge on an electron ⇒ n = Q e = 3 . 2 × 10 - 7 1 . 6 × 10 - 19 = 2 × 10 12 (b) We know, mass of an electron, m e = 9 . 1 × 10 - 31 kg Mass gained by the polythene, M = mass of an electron m e × number of electrons transferred n ⇒ M = m e n = 9 . 1 × 10 - 31 × 2 × 10 12 ⇒ M = 1 . 82 × 10 - 18 kg

The electrostatic force of repulsion between two positive ions carrying equal charges is 4 × 10 - 9 N , when their separation is 5 . How many electrons are missing from each?

Given, force of repulsion between two ions, 4 × 10 - 9 N , c harged ions are separated by a distance, d = 5 Å . Using Coulomb's law, we get, F = k q 2 d 2 . Here, k = 1 4 π ε 0 = 9 × 10 9 N m 2 C - 2 ⇒ 4 × 10 - 9 = 9 × 10 9 q 2 5 × 10 - 10 2 ⇒ q = 3 . 33 × 10 - 19 C Now, using principle of quantization of charge, ⇒ q = n e ⇒ n = q e n = 3 . 33 × 10 - 19 C 1 .6 × 10 - 19 C = 2 Hence, the number of electrons missing from each ion is 2 .

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Three parallel metallic plates, each area $A$ are kept as shown in the figure and charges $Q_{1}$ , $Q_{2}$ and $Q_{3}$ are given to them. Edge effects are negligible. Calculate the charges on the two outermost surfaces $a$ and $f$ .

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Important Questions on Electrostatics

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 1

A polythene piece rubbed with wool is found to have a negative charge of $3.2 \times 10^{- 7} C$ . Find the>

(a) number of electrons transferred.

(b) mass gained by the polythene.

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

Two identical metal spheres $A$ and $B$ placed in contact are supported on insulating stand. What kinds of charge will $A$ and $B$ develop when a negatively charged ebonite rod is brought near $A$ ?

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

Two identical metal spheres carry charges of $+ q$ and $- 2 q$ respectively. When the spheres are separated by a large distance $r$ , the force between them is $F$ . Now the spheres are allowed to touch and then moved back to the same separation. Find the new force of repulsion between them.

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Beta Question Bank for Medical: Physics>Chapter 22 - Electrostatics>BEGINNER'S BOX - 2>Q 4

The electrostatic force of repulsion between two positive ions carrying equal charges is

4 \times 10^{- 9} N

, when their separation is

5

. How many electrons are missing from each?

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

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.

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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

50 %

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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 $3.6 N$ , then

(i) calculate the charge on each sphere, and

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

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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?

Three parallel metallic plates, each area A are kept as shown in the figure and charges Q1, Q2 and Q3 are given to them. Edge effects are negligible. Calculate the charges on the two outermost surfaces a and f.

Important Questions on Electrostatics

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Three parallel metallic plates, each area $A$ are kept as shown in the figure and charges $Q_{1}$ , $Q_{2}$ and $Q_{3}$ are given to them. Edge effects are negligible. Calculate the charges on the two outermost surfaces $a$ and $f$ .