Question

A wire made from tungsten is 4.5 m long and 0.45 mm in diameter. What is its resistance at 1500°C?

Answer 1

Length of the tungsten wire l = 4.5 meters

Diameter of the tungsten wire d = 0.45 mm or 0.00045 meters

Resistivity of of tungdten wire at 1500⁰ C = 40.36 10 ^{- 6} ohm-cm OR O.4036 10 ^{- 6} ohm-meter

Resistance R = ( l / A )

where , = resistivity of the wire in ohm-meter

l = length of the wire in meters

A = Area of the wire in meter²

= / 4 (diameter)²

= / 4 ( 0.00045 )²

= 1.59 10 ^{- 7} m²

  R = ( l / A )

= O.4036 10 ^{- 6} ( 4.5 / 1.59 10 ^{- 7})

= 11.423 Ohms

Resistance of the tungsten wire at 1500^o C R = 11.423 Ohms