SPECIFIC PROPERTIES OF CHARGE
• Charge is a scalar quantity : It represents excess or deficiency of electrons.
• Charge is transferable : If a charged body is put in contact with an another body, then charge can be transferred to another body.
• Charge is always associated with mass
Charge cannot exist without mass though mass can exist without charge.
→ So the presence of charge itself is a convincing proof of existence of mass.
→ In charging, the mass of a body changes.
→ When body is given positive charge, its mass decreases.
→ When body is given negative charge, its mass increases.
• Charge is quantised
The quantization of electric charge is the property by virtue of which all free charges are integral multiple of a basic unit of charge represented by e. Thus charge q of a body is always given by
q = ne, n = positive integer or negative integer
The quantum of charge is the charge that an electron or proton carries.
Note : Charge on a proton = (–) charge on an electron = 1.6 × 10–19 C
Charge is conserved
In an isolated system, total charge does not change with time, though individual charge may change i.e. charge can neither be created nor destroyed. Conservation of charge is also found to hold good in all types of reactions either chemical (atomic) or nuclear. No exceptions to the rule have ever been found.
Charge is invariant
Charge is independent of frame of reference. i.e. charge on a body does not change whatever be its speed.
Charges on a conductor
Static charges reside on the surface of the conductor.
Distribution of charges
The concentration of the charge is more on a surface with greater curvature.
Questions For You:
Two identical metallic spheres of exactly equal masses are taken, one is given a positive charge q and the other an equal negative charge. Their masses after charging are different. Comment on the statement.