Physics · Electric Charges And Fields · NEET
No. Charge is the property carried by particles like electrons and protons. Electricity (current) is charge that is moving. A comb rubbed on hair holds static charge but there is no current until that charge flows. For NEET, this chapter is about charges at rest (electrostatics), not flowing current.
It depends only on electrons. A body is negative if it has extra electrons and positive if it has lost electrons. Protons never move. So when you rub two bodies, electrons transfer from one to the other. The one that gains electrons becomes negative; the one that loses them becomes positive.
The glass rod loses electrons to the silk, so the glass rod becomes positive and the silk becomes negative. Rule of thumb for NEET: glass rod + silk = glass positive; ebonite (or plastic) + wool/fur = ebonite negative. The names 'positive' and 'negative' were fixed by convention from Benjamin Franklin.
Yes, in the sense that positive charge means missing electrons, not extra protons moving. A body becomes positive by giving away electrons. Charge itself always comes in whole units of e = 1.6 x 10^-19 C (this is quantisation). You cannot have half an electron's charge on a normal body.
Two charges of the same sign push apart; two of opposite sign pull together. This is an experimental fact shown by the glass rod and silk experiment: two charged glass rods repel, glass and silk attract. The strength of this push or pull is given later by Coulomb's law, but the direction (attract vs repel) is set by the signs.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Electric charge is a property of matter that causes a force of attraction or repulsion between objects. It comes in two types, positive and negative, and its SI unit is the coulomb (C).
Positive charge (as on a glass rod rubbed with silk) and negative charge (as on plastic rubbed with wool). Like charges repel and unlike charges attract.
Charge is a scalar quantity. It has magnitude and a sign (+ or -) but no direction. That is why charges simply add up algebraically.
The SI unit is the coulomb (C) and charge is written as q or Q. The smallest free charge is that of an electron, e = 1.6 x 10^-19 C.
It is the base of the whole Electric Charges and Fields chapter. Coulomb's law, electric field, dipoles and Gauss's law all start from the idea of positive and negative charge, so this concept is tested indirectly in many questions.
