Physics - Electric Charges Fields - Quiz-2

Two spherical conductors B and C having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance. A third spherical conductor having same radius as that of B but uncharged is brought in contact with B, then brought in contact with C and finally removed away from both. The new force of repulsion between B and C is

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F/4
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3 F/4
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F/8
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3 F/8

Two equally charged, identical metal spheres A and B repel each other with a force 'F'. The spheres are kept fixed with a distance 'r' between them. A third identical, but uncharged sphere C is brought in contact with A and then placed at the mid-point of the line joining A and B. The magnitude of the net electric force on C is

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F
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3F/4
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F/2
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F/4

An infinite number of charges, each of charge 1 μC, are placed on the x-axis with co-ordinates x = 1, 2, 4, 8, ....∞. If a charge of 1 C is kept at the origin, then what is the net force acting on 1 C charge?

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9000 N
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12000 N
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24000 N
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36000 N

A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium, if q is equal to

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$- \frac{Q}{2}$
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$- \frac{Q}{4}$
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$+ \frac{Q}{4}$
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$+ \frac{Q}{2}$

The figure shows the electric lines of force emerging from a charged body. If the electric fields at A and B are E_A and E_B respectively and if the distance between A and B is r, then:

_{B}\)
_{B}\)

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\(E_{A}~>~E
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\(E_{A}~<~E
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$E_{A}~=~\frac{E_{B}}{r^{}}$
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$E_{A}~=~\frac{E_{B}}{r^{2}}$

ABC is an equilateral triangle. Charges +q are placed at each corner. The electric intensity at O will be

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$\frac{1}{4 π ε_{0}} \frac{q}{r^{2}}$
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$\frac{1}{4 π ε_{0}} \frac{q}{r}$
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Zero
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$\frac{1}{4 π ε_{0}} \frac{3 q}{r^{2}}$

The magnitude of electric field intensity E is such that, an electron placed in it would experience an electrical force equal to its weight is given by

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mge
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$\frac{m g}{e}$
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$\frac{e}{m g}$
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$\frac{e^{2}}{m^{2}} g$

A charge particle is free to move in an electric field. It will travel

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Always along a line of force
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Along a line of force, if its initial velocity is zero
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Along a line of force, if it has some initial velocity in the direction of an acute angle with the line of force
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None of the above

An uncharged sphere of metal is placed in between two charged plates as shown. The lines of force look like

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A
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B
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C
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D

The electric field near a conducting surface having a uniform surface charge density σ is given by

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$\frac{σ}{ε_{0}}$ and is parallel to the surface
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$\frac{2 σ}{ε_{0}}$ and is parallel to the surface
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$\frac{σ}{ε_{0}}$ and is normal to the surface
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$\frac{2 σ}{ε_{0}}$ and is normal to the surface

The magnitude of electric field E in the annular region of a charged cylindrical capacitor

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Is same throughout
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Is higher near the outer cylinder than near the inner cylinder
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Varies as 1/r, where r is the distance from the axis
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Varies as 1/r², where r is the distance from the axis

A metallic solid sphere is placed in a uniform electric field. The lines of force follow the path(s) shown in figure as

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1
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2
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3
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4

The figure shows some of the electric field lines corresponding to an electric field. The figure suggests

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E_A > E_B > E_C
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E_A = E_B = E_C
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E_A = E_C > E_B
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E_A = E_C < E_B

A hollow insulated conducting sphere is given a positive charge of 10μC. What will be the electric field at the centre of the sphere if its radius is 2 meters

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Zero
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5 μCm^–2
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20 μCm^–2
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8 μCm^–2

An electron of mass m_e initially at rest moves through a certain distance in a uniform electric field in time t₁. A proton of mass m_p also initially at rest takes time t₂ to move through an equal distance in this uniform electric field. Neglecting the effect of gravity, the ratio of t₂/ t₁ is nearly equal to

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1
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${(m_{p} / m_{e})}^{1 / 2}$
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${(m_{e} / m_{p})}^{1 / 2}$
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1836

Point charges +4q, –q and +4q are kept on the x-axis at points x = 0, x = a and x = 2a respectively, then:

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only -q is in stable equilibrium.
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none of the charges are in equilibrium.
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all the charges are in unstable equilibrium.
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all the charges are in stable equilibrium.

Three identical positive point charges, as shown are placed at the vertices of an isosceles right angled triangle. Which of the numbered vectors coincides in direction with the electric field at the mid-point M of the hypotenuse

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4
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1
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2
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3

Which of the following is incorrect about electrostatic force?

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1 it is conservtive
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2 it is a central force
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3 Eletrostatic field line never intersect
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4 it also epends on the mass content of the body

The figures below show regular hexagons, with charges at the vertices. In which of the following cases the electric field at the centre is not zero?

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1
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2
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3
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4

An electron enters an electric field with its velocity in the direction of the electric lines of force. Then:

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the path of the electron will be a circle.
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the path of the electron will be a parabola.
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the velocity of the electron will decrease.
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the velocity of the electron will increase.

Two small spherical balls each carrying a charge Q = 10 μC (10 micro-coulomb) are suspended by two insulating threads of equal lengths 1m each, from a point fixed in the ceiling. It is found that in equilibrium threads are separated by an angle 60° between them, as shown in the figure. What is the tension in the threads (Given: $\frac{1}{(4 π ε_{0})} = 9 \times 10^{9} N m / C^{2}$ )

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18 N
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1.8 N
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0.18 N
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None of the above

An electron having charge ‘e’ and mass ‘m’ is moving in a uniform electric field E. Its acceleration will be

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$\frac{e^{2}}{m}$
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$\frac{E^{2} e}{m}$
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$\frac{e E}{m}$
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$\frac{m E}{e}$

Infinite charges of magnitude q each are lying at x =1, 2, 4, 8... meter on X-axis. The value of the intensity of the electric field at point x = 0 due to these charges will be

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12 × 10⁹q N/C
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Zero
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6 × 10⁹q N/C
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4 × 10⁹q N/C

A pendulum bob of mass $30 .7 \times 10^{- 6} k g$ and carrying a charge $2 \times 10^{- 8} C$ is at rest in a horizontal uniform electric field of 20000 V/m. The tension in the thread of the pendulum is $(g = 9 .8 m / s^{2})$

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$3 \times 10^{- 4} N$
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$4 \times 10^{- 4} N$
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$5 \times 10^{- 4} N$
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$6 \times 10^{- 4} N$

A charged ball B hangs from a silk thread S, which makes an angle θ with a large charged conducting sheet P, as shown in the figure. The surface charge density σ of the sheet is proportional to

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sin θ
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tan θ
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cos θ
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cot θ

Two-point charges +8q and –2q are located at x = 0 and x = L respectively. The location of a point on the x-axis at which the net electric field due to these two point charges is zero is

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8 L
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4 L
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2 L
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$\frac{L}{4}$

Three infinitely long charge sheets are placed as shown in the figure. The electric field at point P is

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$\frac{2 σ}{ε_{o}} \hat{k}$
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$- \frac{2 σ}{ε_{o}} \hat{k}$
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$\frac{4 σ}{ε_{o}} \hat{k}$
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$- \frac{4 σ}{ε_{o}} \hat{k}$

Two infinitely long parallel conducting plates having surface charge densities +σ and –σ respectively, are separated by a small distance. The medium between the plates is a vacuum. If ε₀ is the dielectric permittivity of vacuum, then the electric field in the region between the plates is

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$0 v o l t s / m e t e r$
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$\frac{σ}{2 ε_{o}} v o l t s / m e t e r$
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$\frac{σ}{ε_{o}} v o l t s / m e t e r$
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$\frac{2 σ}{ε_{o}} v o l t s / m e t e r$

Four-point +ve charges of the same magnitude (Q) are placed at four corners of a rigid square frame as shown in the figure. The plane of the frame is perpendicular to Z-axis. If a –ve point charge is placed at a distance z away from the above frame (z<<L) then

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– ve charge oscillates along the Z-axis.
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It moves away from the frame
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It moves slowly towards the frame and stays in the plane of the frame
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It passes through the frame only once.

A cylinder of radius R and length L is placed in a uniform electric field E parallel to the cylinder axis. The total flux for the surface of the cylinder is given by

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$2 π R^{2} E$
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$π R^{2} / E$
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$(π R^{2} - π R) / E$
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Zero

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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