Two spheres A and B of exactly same mass are given equal positive and negative charges respectively. Their masses after charging

Solution
A loses electrons and B gains electrons. Therefore,mass of A
Which of the following is the best insulator of electricity?

Solution
Ebonite is the best insulator.
Coulomb’s law is true for

Solution
Coulomb’s law is true for all distances small and large. Hence it is called a long range force.
On charging by conduction,mass of a body may

Solution
On charging by conduction, body may gain mass,if it acquires negative charge. It may lose mass, if it acquires positive charge.
If a body is positively charged, then it has

Solution
Positive charge is due to deficiency of electrons
When a body is charged by induction, then the body

Solution
Charging by induction involves transfer of charges from one part to the other of the body. No loss of charge is involved.
The core of a transformer is laminated because

Solution
When there is change of flux in the core of a transformer due to change in current round it,eddy current is produced. The direction of this current is opposite to the current which produces it, so it will reduce the main current. We laminate the core so that flux is reduced resulting in the reduced production of eddy current.
Alternating current cannot bemeasured by D.C. ammeter because

Solution
D.C. ammeter measures average current in AC current,average current is zero for complete cycle. Hence reading will be zero.
In an A.C. circuit with voltage V and current I the power dissipated is

Solution
Power dissipated=E_{rms}. I_{rms}=(E_{rms})(I_{rms}) cosθ Hence, power dissipated depends upon phase difference.
A bulb and a capacitor are connected in series to a source of alternating current. If its frequency is increased, while keeping the voltage of the source constant, then bulb will