• Charge is a fundamental particle in an atom. It may be positive or negative.
• Like charges repel each other.
• Unlike charges attract each other.
Coulomb (C) : S. I. unit of charge
1 Coulomb charge = Charge present on approx. 6 × 10^18 electrons
• Charge on 1 electron = Negative charge of 1.6 × 10^−19 C
Q = ne
Where Q = Charge (total)
n = No. of electrons
e = Charge on 1 electron
Current (I) : The rate of flow of charge is called current.
Current = Charge / Time
I = Q/T
S. I. unit of current = Ampere (A)
1 A = 1 Cs−1
1 mA = 10^−3 A
1 μA = 10^−6 A
Current is measured by Ammeter.