Physics - Electric Charges Fields - Quiz-4

Suppose the charge of a proton and an electron differ slightly. One of them is -e and the other is $(e + ∆ e)$ . If the net of electrostatic force and gravitaional force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero,then $∆ e$ is of the order [Given mass of hydrogen, $m_{h}$ =1.67 $\times 10^{- 27}$ kg]

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() $10^{- 20} C$
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() $10^{- 23} C$
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() $10^{- 37} C$
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() $10^{- 47} C$

Two identical charged spheres suspended from a common point by two massless strings of lengths l are initially at a distance d(d < < l) apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity v. Then, v varies as a function of the distance x between the sphere, as:

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() $v \propto x$
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() $v \propto x^{\frac{-1}{2}}$
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() $v \propto x^{-1}$
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() $v \propto x^{\frac{1}{2}}$

Two pith balls carrying equal charges are suspended from a common point by strings of equal length, the equilibrium separation between them is r. Now the strings are rigidly clamped at half the height. The equilibrium separation between the balls now become:

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(1/√2)²
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$(r / \sqrt[3]{2})$
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(2r/√3)
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(2r/3)

What is the flux through a cube of side 'a' if a point charge q is at one of its corners?

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$\frac{2 q}{ε_{0}}$
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$\frac{q}{8 ε_{0}}$
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$\frac{q}{ε_{0}}$
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$\frac{q}{2 ε_{0}} 6 a^{2}$

A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled, then the outward electric flux will

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be reduced to half
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remain the same
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be doubled
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increase four times

Two positive ions, each carrying a charge q, are separated by a distance d. If F is the force of repulsion between the ions, the number of electrons missing from each ion will be (e being the charge on an electron)

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$\frac{4 {πε}_{\circ} {Fd}^{2}}{e^{2}}$
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$\sqrt{\frac{4 {πε}_{\circ} {Fe}^{2}}{d^{2}}}$
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$\sqrt{\frac{4 {πε}_{\circ} {Fd}^{2}}{e^{2}}}$
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$\frac{4 {πε}_{\circ} {Fd}^{2}}{q^{2}}$

A surface of side L metre in the plane of the paper is placed in a uniform electric field E(volt/m) acting along the same plane at an angle $θ$ with the horizontal side of the square as shown in figure. The electric flux linked to the surface in unit of V-m, is

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EL²
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EL²cos $θ$
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EL²sin $θ$
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0

Two parallel metal plates having charges +Q and -Q faces each other at a certain distance between them. If the plates are now dipped in kerosene oil tank, the electric field between the plates will

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become zero
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increase
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decrease
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remain same

The electric field at a distance $\frac{3 R}{2}$ from the centre of a charged conducting spherical shell of radius R is E. The electric field at a distance $\frac{R}{2}$ from the centre of the sphere is

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$zero$
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$E$
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$\frac{E}{2}$
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$\frac{E}{3}$

A thin conducting ring of radius R is given a charge +Q. The electric field at the centre O of the ring due to the charge on the part AKB of the ring is E. The electric field at the centre due to the charge on the part ACDB of the ring is

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3E along KO
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E along OK
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E along KO
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3E along OK

There is a uniform electric field of strength 10³ V/m along the y-axis. A body of mass 1g and charge 10^–6C is projected into the field from the origin along the positive x-axis with a velocity 10m/s. Its speed in m/s after 10s is (Neglect gravitation)

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10
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$5 \sqrt{2}$
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$10 \sqrt{2}$
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20

Six charges, three positive and three negative of equal magnitude are to be placed at the vertices of a regular hexagon such that the electric field at O is double the electric field when only one positive charge of same magnitude is placed at R. Which of the following arrangements of charges is possible for P, Q, R, S, T and U respectively

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+, –, +, –, –, +
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+, –, +, –, +, –
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+, +, –, +, –, –
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–, +, +, –, +, –

A charge of magnitude 3e and mass 2m is moving in an electric field E. The acceleration imparted to the charge is

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3Ee / 2m
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2Ee / 3m
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2m / 3Ee
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3m / 2Ee

An electron falls from rest through a vertical distance h in a uniform and vertically upward-directed electric field E. The direction of the electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest through the same vertical distance h. The fall time of the electron in comparison to the fall time of the proton is:

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smaller.
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5 times greater.
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10 times greater.
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equal.

A toy car with charge q moves on a frictionless horizontal plane surface under the influence of a uniform electric field $\vec{E}$ . Due to the force q $\vec{E}$ , its velocity increases from 0 to 6 m/s in one-second duration. At that instant, the direction of the field is reversed. The car continues to move for two more seconds under the influence of this field. The average velocity and the average speed of the toy car between 0 to 3 seconds are respectively:-

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2 m/s, 4 m/s
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1 m/s, 3 m/s
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1 m/s, 3.5 m/s
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1.5 m/s, 3 m/s

Two identical charged spheres suspended from a common point by two massless strings of lengths l, are initially at a distance d (d << l) apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity v. Then, v varies as a function of the distance x between the sphere, as

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v $\propto$ x
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v $\propto$ $x^{- 1 / 2}$
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v $\propto$ $x^{- 1}$
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v $\propto$ $x^{1 / 2}$

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$\frac{r}{3\sqrt2}$
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$\frac{r}{2\sqrt2}$
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$\frac{2r}{3}$
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None of the above

A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled, then the outward electric flux will

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be reduced to half
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remain the same
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be doubled
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increased four times

The mean free path of electrons in a metal is 4 x 10^-8 m. The electric field which can give on an average 2 eV energy to an electron in the metal will be in the unit of Vm^-1

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8 x 10⁷
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5 x 10^-11
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8 X 10^-11

5 X 10⁷

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3E along KO
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E along OK
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E along KO
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3 E along OK

Three-point charges + q and -2q and +q are placed at points (x=0, y=a, z=0), (x=0, y=0, z=0) and (x=a, y=0, z=0), respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are:

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$\sqrt{2}$ qa along +y direction
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$\sqrt{2}$ qa along the line joining points (x=0, y= 0, z=0) And (x=a, y=a, z=0)
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qa along the line joining points (x=0, y=0, z=0) And (x=a, y=a, z=0)
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$\sqrt{2}$ qa along +x direction

A hollow cylinder has a charge q coulomb within it(at the geometrical centre). If ϕ is the electric flux in unit of Volt-meter associated with the curved surface B, the flux linked with the plane surface A in unit of Volt-meter will be:

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$\frac{1}{2} (\frac{q}{ε_{0}} - Φ)$
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$\frac{q}{2 ε_{0}}$
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$\frac{Φ}{3}$
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$\frac{q}{ε_{0}} - Φ$

Find electric field due to a uniformly charged, long and thin rod

[This question includes concepts from 12th syllabus]

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$\frac{k λ}{r}$
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$\frac{k λ}{2 r}$
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$\frac{2 k λ}{r}$
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$\frac{k λ}{4 r}$

A hollow metal sphere of radius R is uniformly charged. The electric field due to the sphere at a distance r from the centre:

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decreases as r increases for r < R and for r > R.
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increases as r increases for r < R and for r > R.
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zero as r increases for r < R, decreases as r increases for r > R.
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zero as r increases for r < R, increases as r increases for r > R.

Two point charges A and B, having charges +Q and -Q respectively, are placed at certain distance apart and force acting between them is F. If 25% charge of A is transferred to B, then force between the charges becomes:

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$\frac{4 F}{3}$
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$F$
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$\frac{9 F}{16}$
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$\frac{16 F}{9}$

Two parallel infinite line charges with linear charge densities $+ λ C / m a n d + λ C / m$ are placed at a distance R. The electric field mid-way between the two line charges is:

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$\frac{λ}{2 {πε}_{0} R} N / C$
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zero
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$\frac{2 λ}{{πε}_{0} R} N / C$
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$\frac{λ}{{πε}_{0} R} N / C$

A sphere encloses an electric dipole with charges $\pm 3 \times 10^{- 6} C$ . What is the total electric flux through the sphere?

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-3 $\times 10^{- 6}$
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zero
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3 $\times 10^{- 6} N m^{2} / C$
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6 $\times 10^{- 6} N m^{2} / C$

The figure shows some of the equipotential surfaces. Magnitude and direction of the electric field is given by

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200 V/m, making an angle $120^{\circ}$ with the x-axis
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100 V/m, pointing towards negative x-axis
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200 V/m, making an angle $- 60^{\circ}$ with the x-axis
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100 V/m, making an angle $30^{\circ}$ with the x-axis

Electric field in a region is increasing in magnitude along x-direction. The equipotential surfaces associated are :

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Planes parallel to xy-plane
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Planes parallel to yz-plane
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Co-axial cylinders around the x-axis
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All of these

If a unit positive charge is taken from one point to another on an equipotential surface, then

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Work is done on the charge
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Work is done by the charge
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Potential energy of the charged is changed
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No work is done on the charge

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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