Resistance of a Wire (CIE IGCSE Physics)

• As electrons pass through a wire, they collide with the metal ions in the wire

Electrons collide with ions, which resist their flow

• The ions get in the way of the electrons, resisting their flow

• If the wire is longer, each electron will collide with more ions and so there will be more resistance:

The longer a wire, the greater its resistance

• If the wire is thicker (greater diameter) there is more space for the electrons and so more electrons can flow:

The thicker a wire, the smaller its resistance

EXTENDED

• The relationship between resistance, length and cross-sectional area can be represented mathematically

• • Resistance is directly proportional to length

• • Resistance is inversely proportional to cross-sectional area (width, or thickness) 

The mathematical relationship between length and width of the wire and the resistance