A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 10^3 N/C and points radially inward, what is the net charge on the sphere? - Physics


A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 10N/C and points radially inward, what is the net charge on the sphere?



Electric field intensity (E) at a distance (d) from the centre of a sphere containing net charge q is given by the relation,

`"E" = "q"/(4piin_0"d"^2)`


q = Net charge = 1.5 × 103 N/C

d = Distance from the centre = 20 cm = 0.2 m

0 = Permittivity of free space

And, `1/(4piin_0)` = 9 × 109 N m2 C−2

∴ `"q" = "E"(4piin_0)"d"^2`

= `(1.5xx10^3xx(0.2)^2)/(9xx10^9)`

= 6.67 × 109 C

= 6.67 nC

Therefore, the net charge on the sphere is 6.67 nC.

  Is there an error in this question or solution?
Chapter 1: Electric Charges and Fields - Exercise [Page 48]


NCERT Physics Class 12
Chapter 1 Electric Charges and Fields
Exercise | Q 1.21 | Page 48
NCERT Physics Class 12
Chapter 1 Electric Charge and Fields
Exercise | Q 21 | Page 48

Video TutorialsVIEW ALL [2]


How does Ampere-Maxwell law explain the flow of current through a capacitor when it is being charged by a battery? 

Write the expression for the displacement current in terms of the rate of change of electric flux. 

Mark out the correct options.

A proton and an electron are placed in a uniform electric field.

A charge Q is placed at a distance a/2 above the centre of a horizontal, square surface of edge a as shown in the following figure . Find the flux of the electric field through the square surface.

A long cylindrical volume contains a uniformly distributed charge of density ρ. Find the electric field at a point P inside the cylindrical volume at a distance x from its axis (see the figure).

Two large conducting plates are placed parallel to each other with a separation of 2⋅00 cm between them. An electron starting from rest near one of the plates reaches the other plate in 2⋅00 microseconds. Find the surface charge density on the inner surfaces.

Two large conducting plates are placed parallel to each other and they carry equal and opposite charges with surface density σ as shown in the figure. Find the electric field (a) at the left of the plates (b) in between the plates and (c) at the right of the plates.

Two particles A and B, each with a charge Q, are placed a distance d apart. Where should a particle of charge q be placed on the perpendicular bisector of AB, so that it experiences maximum force? What is the magnitude of this maximum force? 

The electric force experienced by a charge of 1.0 × 10−6 C is 1.5 × 10−3 N. Find the magnitude of the electric field at the position of the charge.

A positive charge Q is distributed uniformly over a circular ring of radius R. A particle of mass m, and a negative charge q, is placed on its axis at a  distance x from the centre. Find the force on the particle. Assuming x << R, find the time period of oscillation of the particle if it is released from there . 

A rod of length L has a total charge Q distributed uniformly along its length. It is bent in the shape of a semicircle. Find the magnitude of the electric field at the centre of curvature of the semicircle. 

A positively charged glass rod is brought close to a metallic rod isolated from ground. The charge on the side of the metallic rod away from the glass rod will be ______.

Choose the correct option.

An electron is placed between two parallel plates connected to a battery. If the battery is switched on, the electron will

Choose the correct option.

A charge of + 7 μC is placed at the centre of two concentric spheres with radius 2.0 cm and 4.0 cm respectively. The ratio of the flux through them will be

Choose the correct option.

Two point charges of +5 μC are so placed that they experience a force of 8.0 × 10-3N. They are then moved apart so that the force is now 2.0 × 10-3N. The distance between them is now

Answer the following question.

What is the magnitude of the charge on an electron?

Answer the following question.

Two parallel plates have a potential difference of 10V between them. If the plates are 0.5 mm apart, what will be the strength of the electric charge.

Two small spheres 18 cm apart have equal negative charges and repel each other with the force of 6 × 10-3 N. Find the total charge on both spheres.

One metallic sphere A is given a positive charge whereas another identical metallic sphere B of exactly the same mass as A is given an equal amount of negative charge. Then

When 1019 electrons are removed from a neutral metal plate through some process, the electric charge on it is ______

Two small conducting spheres of equal radius have charges +10 µC and -20 µC respectively and placed at a distance R from each other experience force F1· If they are brought in contact and separated to the same distance, they experience force F2. The ratio of F1 to F2 is ____________.

A conducting sphere of radius 0.104 m has an unknown charge. If the electric field at 0.20 m from the centre of the sphere is 1.5 x 103 NC-1 and points radially inward, what is the electric flux?

Electric charges are of ______.

A positively charged rod is brought near an uncharged conductor. If the rod is then suddenly withdrawn, the charge left on the conductor will be ______.

A solid sphere of radius R1 and volume charge density `rho = rho_0/"r"` is enclosed by a hollow sphere of radius R2 with negative surface charge density σ, such that the total charge in the system is zero. `rho_0` is a positive constant and r is the distance from the center of the sphere. The ratio R2/R1 is ______.

Equal charge are given to two-sphere of different radii. The potential will be

Which one of the following is the unit of electric charge?

A metallic spherical shell has an inner radius R1 and outer radius R2. A charge Q is placed at the centre of the spherical cavity. What will be surface charge density on (i) the inner surface, and (ii) the outer surface?

A positive charge particle of 100 mg is thrown in opposite direction to a uniform electric field of strength 1 × 105 NC–1. If the charge on the particle is 40 μC and the initial velocity is 200 ms-1, how much distance it will travel before coming to the rest momentarily ______.

Given below are two statements:

  • Statement I: The electric force changes the speed of the charged particle and hence changes its kinetic energy; whereas the magnetic force does not change the kinetic energy of the charged particle.
  • Statement II: The electric force accelerates the positively charged particle perpendicular to the direction of the electric field. The magnetic force accelerates the moving charged particle along the direction of the magnetic field.

In light of the above statements, choose the most appropriate answer from the options given below.

A certain charge Q is divided into two parts q and (Q - q). How should the charges Q and q be divided so that q and (Q - q) placed at a certain distance apart experience maximum electrostatic repulsion?

Two identical metallic spheres A and B when placed at certain distance in air repel each other with a force of F. Another identical uncharged sphere C is first placed in contact with A and then in contact with B and finally placed at midpoint between spheres A and B. The force experienced by sphere C will be:

A charge of 4 µC is to be divided into two. The distance between the two divided charges is constant. The magnitude of the divided charges so that the force between them is maximum, will be: 

Two identical conducting spheres with negligible volume have 2.1 nC and -0.1 nC charges, respectively. They are brought into contact and then separated by a distance of 0.5 m. The electrostatic force acting between the spheres is ______ × 10-9N.

[Given: 4πε0 = `1/(9xx10^9)` SI unit]

Two identical conducting spheres A and B, carry equal charge. They are separated by a distance much larger than their diameter, and the force between them is F. A third identical conducting sphere, C, is uncharged. Sphere C is first touched to A, then to B, and then removed. As a result, the force between A and B would be equal to ______.

A straight infinitely long cylinder of radius R0 = 10 cm is uniformly charged with a surface charge density σ = + 10-12 C/m2. The cylinder serves as a source of electrons, with the velocity of the emitted electrons perpendicular to its surface. Electron velocity must be ______ × 105 m/s to ensure that electrons can move away, from the axis of the cylinder to a distance greater than r = 103 m.

A particle of mass m and charge q is placed at rest in a uniform electric field E and then released. The kinetic energy gained by the particle after moving a distance of y will be ______.

The electrostatic potential inside a charged spherical ball is given by `Phi = ar^2 + b`, where r is the distance from the centre a, and b are constants. Then the charge density inside the ball is ______.

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

Two particles A and B having the same mass have charges +q and +4q, respectively. When they are allowed to fall from rest through the same electric potential difference the ratio of their speeds vA to vB will become ______.

The potential at a point x (measured in µm) due to some charges situated on the X-axis is given by v(x) = `20/((x^2 - 4)` V. The electric field E at x = 4 µm is given by ______.


      Forgot password?
Use app×