Plz..ans this Q. immediately...
Find the electric field at the centre of the circular ring..
this Q. is related with chapter Electrostatic of class 12
Answers
Page No 119:
Question 1:
The charge on a proton is +1.6 × 10−19 C and that on an electron is −1.6 × 10−19 C. Does it mean that the electron has 3.2 × 10−19 C less charge than the proton?
Answer:
An electron and a proton have equal and opposite charges of magnitude 1.6 × 10−19 C. But it doesn’t mean that the electron has 3.2 × 10−19 C​ less charge than the proton.
Question 2:
Is there any lower limit to the electric force between two particles placed at a separation of 1 cm?
Answer:
Yes, there’s a lower limit to the electric force between two particles placed at a separation of 1 cm, which is equal to the magnitude of force of repulsion between two electrons placed at a separation of 1 cm.
Question 3:
Consider two particles A and B of equal charges placed at some distance. Particle A is slightly displaced towards B. Does the force on B increase as soon as particle A is displaced? Does the force on particle A increase as soon as it is displaced?
Answer:
Electrostatic force follows the inverse square law,
F=kr2. This means that the force on two particles carrying charges increases on decreasing the distance between them. Therefore, as particle A is slightly displaced towards B, the force on B as well as A will increase.
Question 4:
Can a gravitational field be added vectorially to an electric field to get a total field?
Answer:
No, a gravitational field cannot be added vectorially to an electric field.
This is because for electric influence, one or both the bodies should have some net charge and for gravitational influence both the bodies should have some mass. Also, gravitational field is a weak force,while electric field is a strong force.
Question 5:
Why does a phonograph record attract dust particles just after it is cleaned?
Answer:
When a phonograph record is cleaned, it develops a charge on its surface due to rubbing. This charge attracts the neutral dust particles due to induction.
Question 6:
Does the force on a charge due to another charge depend on the charges present nearby?
Answer:
Coulomb’s Law states that the force between two charged particle is given by
F=q1q24π∈0r2,
where
q1 and q2 are the charges on the charged particles
r = separation between the charged particles
∈0= permittivity of free space
According to the Law of Superposition, the electrostatic forces between two charged particles are unaffected due to the presence of other charges.
Question 7:
In some old texts it is mentioned that 4π lines of force originate from each unit positive charge. Comment on the statement in view of the fact that 4π is not an integer.
Answer:
4π is the total solid angle. “4π lines of force” is just a way of stating that the field lines extend uniformly in all directions away from the charge.
Question 8:
Can two equipotential surfaces cut each other?
Answer:
At the point of intersection, two normals can be drawn. Also, we know that electric field lines are perpendicular to the equipotential surface. This implies that at that point two different directions of the electric field are possible, which is not possible physically. Hence, two equipotential surfaces cannot cut each other.
Question 9:
If a charge is placed at rest in an electric field, will its path be along a line of force? Discuss the situation when the lines of force are straight and when they are curved.
Answer:
If a charge is placed at rest in an electric field, its path will be tangential to the lines of force. When the electric field lines are straight lines then the tangent to them will coincide with the electric field lines so the charge will move along them only. When the lines of force are curved, the charge moves along the tangent to them.
Question 10:
Consider the situation shown in the figure. What are the signs of q1 and q2? If the lines are drawn in proportion to the charges, what is the ratio q1/q2?
Figure
Answer:
The electric lines of force are entering charge q1; so, it is negative. On the other hand, the lines of force are originating from charge q​​​2; so, it is positive. If the lines are drawn in proportion to the charges, then
q1q2=618⇒q1q2=136 lines are entering q​​​1 and 18 are coming out of q​​​2.