# Class 10 Physics Electrostatics 12.11 In Bohrs atomic model of hydrogen atom the electron is in an orbit around the nuclear proton at a distance of 5.29 \times 10^{-11} " \mathrm{m} with a speed of 2.18 \times 10^{6} \mathrm{

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##### 12.11 In Bohrs atomic model of hydrogen atom the electron is in an orbit around the nuclear proton at a distance of 5.29 \times 10^{-11} " \mathrm{m} with a speed of 2.18 \times 10^{6} \mathrm{~ms}^{-1} . \left(e=1.60 \times 10^{-10} \mathrm{C}\right. mass of electron \left.=9.10 \times 10^{-31} \mathrm{~kg}\right) . Find(c) The ionization energy for the atom in eV

The electric flux through the surface of a sphere having a point charge at its centre depends upon:A) Surface area of sphereB) Radius of sphereC) Quantity of charge inside the sphereD) None of these

An electric field is most directly related to:A) The momentum of a test chargeB) The kinetic energy of a test chargeC) The potential energy of a test chargeD) The force acting on a test charge

13.4. What is gold leaf electroscope? Discuss its working principle with a labelled diagram.

Three capacitors of capacitance 2 \mu \mathrm{F} each are connected in parallel. Their equivalent capacitance will be:A) 0.66 \mu \mathrm{F} B) 4 \mu \mathrm{F} C) 6 \mu \mathrm{F} D) 1.5 \mu \mathrm{F}

The force experience by a charge 10 \mu \mathrm{C} when placed at a point is 10^{-5} \mathrm{~N} . the electric field intensity at the point is:A) 0.1 \mathrm{NC}^{-1} B) 1 \mathrm{NC} C) 10 \mathrm{NC}^{-1} D) 1 \mathrm{NC}^{-1}

v. According to Coulombs law what happens to the attraction of two oppositely charged objects as their distance of separation increases?(a) increases(b) decreases(c) remains unchanged(d) cannot be determined

13.3. The force of repulsion between two identical positive charges is 0.8 \mathrm{~N} when the charges are 0.1 \mathrm{~m} apart. Find the value of each charge.Ans. \left(9.4 \times 10^{-7} \mathrm{C}\right)

13.10. Two capacitors of capacitances 6 \mu \mathrm{F} and 12 \mu \mathrm{F} are connected in parallel with a 12 \mathrm{~V} battery. Find the equivalent capacitance of the combination. Find the charge and the potential difference across each capacitor.Ans. (18 \mu \mathrm{F} 72 \mu \mathrm{C} 144

The capacitor whose capacitance cannot be changed is called capacitor:A) FixedB) CapacitanceC) DecreaseD) Capacitor

12.9 Do electrons tend to go to region of high potential or of low potential?

Electric intensity at a place due to a charged conductor is a:A) Scalar quantityB) Vector quantityC) Semi vector and semi scalar quantityD) Dimensions quantity

Example 13.1: Two bodies are oppositely charged with 500 \mu \mathrm{C} and 100 \mu \mathrm{C} charge. Find the force between the two charges if the distance between them in air is 0.5 \mathrm{~m} .

viii. Five joules of work is needed to shift 10 \mathrm{C} of charge from one place to another. The potential difference between the places is(a) 0.5 \mathrm{~V} (b) 2 \mathrm{~V} (c) 5 \mathrm{~V} (d) 10 \mathrm{~V}

13.8. A capacitor holds 0.03 coulombs of charge when fully charged by a 6 volt battery. How much voltage would be required for it to hold 2 coulombs of charge?Ans. (400V)

The force between two electrons separated by a distance r varies as:A) \mathrm{r} 2 B) r C) r-1 D) r-2

12.9 A proton placed in a uniform electric field of 5000 \mathrm{NC}^{-1} directed to right is allowed to go a distance of 10.0 \mathrm{~cm} from A to B. Calculate(c) The change in P.E. of proton

Like charges each other:A) AttractB) RepelC) ContractD) None of these

13.6. A point charge of +2 \mathrm{C} is transferred from a point at potential 100 \mathrm{~V} to a point at potential 50 \mathrm{~V} . What would be the energy supplied by the charge?Ans. (100J)

iii. Two uncharged objects A and B are rubbed against each other. When object B is placed near a negatively charged object C the two objects repel each other. Which of the following statements is true about object A?(a) remains unchargedb) becomes positively charged(c) becomes negatively charged (d) unpredictable

When the distance between two charged particles is halved the force between them becomes:A) One-fourthB) One-halfC) DoubleD) Four times

vi. The Coulombs law is valid for the charges which are(a) moving and point charges(b) moving and non-point charges(c) stationary and point charges(d) stationary and large size charges

Electric field intensity is a vector quantity and its direction is:A) Anti parallel to the forceB) Perpendicular to the direction of forceC) Opposite to the direction of forceD) Along the direction of force

13.16. What is difference between variable and fixed type capacitor?

The force experienced by a unit positive charge when placed in an electric field is called:A) Potential of electric field at that pointB) Moment of electric field at that pointC) Intensity of electric field at that pointD) Capacity of electric filed at that point

vii. A positive and a negative charge are initially 4 \mathrm{~cm} apart. When they are moved closer together so that they are now only 1 \mathrm{~cm} apart the force between them is(a) 4 times smaller than before(b) 4 times larger than before(c) 8 times larger than before(d) 16 times larger than before

Example 13.4: Three capacitors with capacitances of 3.0 \mu \mathrm{F} 4.0 \mu \mathrm{F} and 5.0 \mu \mathrm{F} are arranged in series combination to a battery of 6 \mathrm{~V} where 1 \mu \mathrm{F}=10^{-6} \mathrm{~F} . Find(a) the total capacitance of the series combination.(b) the quantity of charge across each capacitor.(c) the voltage across each capacitor.