Physics Notes - Electricity

Definition of Electricity

Electricity is the flow of electric charge, typically through a conductor like a wire. It is used to power devices and transfer energy.

Formula: V = I × R

Example 1:
A resistor has R = 5 Ω and I = 2 A. Find V.
Solution: V = 2 × 5 = 10 V

Example 2:
A bulb uses 12 V and has R = 6 Ω. Find I.
Solution: I = 12 / 6 = 2 A

Resistance is the property of a material that opposes the flow of electric current.

Formula: R = V / I or R1/R2 ×R1/R2

Example:
V = 10 V, I = 2 A → R = 10 / 2 = 5 Ω

Ohmic Materials: Obey Ohm’s Law. Current increases linearly with voltage.
Examples: Copper, Nichrome
Non-Ohmic Materials: Do not obey Ohm’s Law. Current does not increase linearly.
Examples: Filament bulb, diode

Graph 1: Ohmic Material (Copper)
A straight line showing constant resistance.
Current increases proportionally with voltage.

Graph 2: Non-Ohmic Material (Filament Bulb)
A curved line showing increasing resistance.
Current increases slowly as voltage rises.