The SI unit of electric field intensity is 

Electric field intensity (E) due to an electric dipole varies with distance (r) of the point from the centre of dipole as:

Electrostatic potential V at a point, distant r from a charge q varies as

1 stat-Coulomb = ......... Coulomb

If \(\oint _{ s }^{ }{ E.ds } =0\) over a surface, then

Two small balls having equal positive charge q coulomb are suspended by two insulating strings of equal length l metre from a hook fixed to a stand. The whole set up is taken in a satellite into space where there is no gravity. What is the angle between the two strings and the tension in each string?

Two point charges of +2 \(\mu C\) and +6 \(\mu C\) repel each other with a force of 12N. If each is given an additional charge of -4\(\mu C\) , what will be the new force?

State superposition principle for electrostatic force on a charge due to a number of charges.

A charged Particle q is shot towards another charged particle Q which is fixed , with a speed v. It approaches Q up to a closet distance r and then returns, If q were given a speed 2 v the n find the closet distance of approach.

What is the force between two small charged spheres having charges of 2 \(\times\) 10^-7C and 3 \(\times\) 10^-7C placed 30 cm apart in air?

In a parallel plate capacitor with air between the plates, each plate has an area of 6\(\times\)10^-3m² and the distance between the plates is 3 mm. Calculate the capacitance if this capacitor. If this capacitor is connected to a 100 V supply, what is the charge on each plate of the capacitor?

(a) conductor A with a cavity as shown in figure.
(i) is given a charge Q. Show that the entire charge must appear on the outer surface of the conductor.
(ii) Another conductor B with charge q is inserted into the cavity keeping B insulated from A. Show that the total charge on the outside surface A is Q + q Figure.
(iii) A sensitive instrument is to be shifted from the strong electrostatic field in its environment. Siggest a possible way.

A 4 μF capacitor is charged by a 200V supply is then disconnected and the charged capacitor is connected to another uncharged 2 μF capacitors. How much electrostatic energy of the first capacitor is in the form of heat and electromagnetic radiation?

Why does a charged glass rod attract a piece of paper?

A physics teacher tells his students in the class that in paramagnetic materials, every atom has some permanent magnetic dipole moment. In the absence of an external magnetic field, the atomic dipoles are randomly oriented so that average magnetic moment per unit volume of the material behaves as a magnet. When an external magnetic field is applied, the torque developed tries to align the atomic magnetic dipoles in the direction of the field. That is why the specimen gets magnetized weekly in the direction of the field.
Read the above passage and answer the following questions:
(i) Name any three paramagnetic materials
(ii) Name any two ferromagnetic materials. How is their behavior different from that of paramagnetic materials?
(iii) The teacher asks the students how true is the famous saying: 'Spare the rod and spoil the child', comment.

As it is known that all matter is made up of atoms/ molecules. Every atom consists of a central core, called the atomic nucleus, around which negatively charged electrons revolve in circular orbits. Every atom is electrically neutral containing as many electrons as the number of protons in the nucleus. All the materials are electrically neutral, they contain charges, but their charges are exactly balanced.
Read the above passage and answer the following questions.
Everybody whether a conductor or an insulator is electrically neutral. Is it true?
Charging lies in charge imbalance, i.e. excess charge or deficit charge, comment.
How do you visualise this principle being applied in our daily life?

An elderly woman went alone to Registrar's office to disburse her property. When she enquired in the office she was asked to get a xerox copy of the do ment which works under electrostatic induction. The xerox shop was far away and across the road. She took the help of a passer-by and got her xerox done.
(a) What values did the passer-by have?
(b) How does a neutral body get charged by electrostatic induction?

Two capacitors \(3\mu F\) and \(6\mu F\) are connected in series with a 6V battery. A cross which of the capacitors will there be larger potential difference?