Chapter-12

Electricity

• 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.