• The concept of charge dates back to ancient Greece, where Thales observed static electricity by rubbing amber with fur around 600 BEC.
• Static electricity can be observed in various ways. For example when clothes are removed from a dryer , they cling together because electric charged are transferred between the clothes.
• When we brush our hair both hair and brush become charged .
• Static electric charge :- A stationary electric charge typically produced by friction which causes sparks or cracking or the attraction of dust or hairs.
• Electric charge :- Electric charge is the basic properties of matter due to which it experience a force when kept in an electric field or magnetic field .
• Electric charge is denoted by Q or q .
• It a scalar quantity .
• Its SI unit is Coulomb ( C ).
• cgs unit is stat coulomb.
  $\mathrm{<b>1</b>}\mathrm{<b>C</b>}<b>=</b>\mathrm{<b>3</b>}<b>\times </b>{\mathrm{<b>10</b>}}^{\mathrm{<b>9</b>}}\mathrm{<b>s</b>}\mathrm{<b>t</b>}\mathrm{<b>a</b>}\mathrm{<b>t</b>}<b> </b>\mathrm{<b>c</b>}\mathrm{<b>o</b>}\mathrm{<b>u</b>}\mathrm{<b>l</b>}\mathrm{<b>o</b>}\mathrm{<b>m</b>}\mathrm{<b>b.</b>}$

* Properties of electric charge *

1. Only two types of charge is possible  either positive or negative .
2. Like charge repel and unlike charge attract each other
3. Quantization of electric charge :- It state that electric charge on a body can only be exist in the integral multiple of electrons transferred ,it cannot be fractional.   Q = ne , where , n= number of electrons = 1,2,3,4,5……….  ,  Q = charge ,  e = charge on an electron.
4. Additive property of charge  :- Total charge on a body is algebraic sum of charges present at its different portions.
5. Law of conservation of charge :- It state that electric charge can neither be created nor be destroyed but it an be transferred from one body to another body , total charge of a system is always conserved.

• Charge is always associated with mass .

• Loss of electrons of electrons gives positive charge . number of protons > number of electrons.

• • •  Gain of electrons gives negative charge. number of protons < number of electrons .
    •  when an object is negatively charged ,it gains electros and therefore its mass increases negligibly .
    • When an object is positively charged it losses electrons and therefore its mass decreases .
    • Smaller unit of charge
    $\mathrm{ \; \; 1}milli coulomb=1mC=1\times {10}^{–3}C$
    $\mathrm{<i>1m</i>}icro coulomb = 1\mu C=1\times {10}^{–6}C$
    $1nano coulomb=1nC=1\times {10}^{–9}C$
    $1pico coulomb = \mathrm{1p}C= 1\times {10}^{–12}C\mathrm{<br>}\mathrm{<br>}\mathrm{<br>}\mathrm{<br>}\mathrm{<br>}\mathrm{<br>}\mathrm{<br>}\mathrm{<br>}$
  • $Charge on an electron=–1.6\times {10}^{–19}C.$
  • $Mass of an electron =9.11\times {10}^{–31}kg=9.11\times {10}^{–28}g$
  • $Charge on a proton=+1.6\times {10}^{–19}C$
  • $Mass of a proton=1.67\times {10}^{–27}kg=1.67\times {10}^{–24}g$
  • $Charge on a neutron=chargeless\left(neutral\right)$
  • $Mass of a neutron=1.67\times {10}^{–27}kg=1.67\times {10}^{–24}g$
  • Atoms are electrically neutral because the number of negatively charged particles electron and positively  charged particles proton are equal in an atom.