A potential difference of 18 V is maintained between the end

A potential difference of 1.8 V is maintained between the ends of a 2700 cm length of wire whose diameter is 0.66 mm. The conductivity of the wire is 5.80 Times 10^7 (ohm.m)^-1. Determine the rate at which energy in the wire is transformed from kinetic to thermal energy. 8.26 W 5.19 J 3.38 J 2.38 W. 5.19 W.

Solution

resistivity

p =1/conductivity =1/(5.8*10⁶) =1.724*10^-8 ohm-m

Area

A=pi*D²/4 =pi*(0.66*10^-3)²/4 =3.42*10^-7 m²

Resistance

R=pL/A =(1.724*10^-8)*2700*10^-2/(3.42*10^-7)

R=1.36 ohms

The rate at which energy is transformed from kinetic to thermal energy is

P=V²/R =1.8²/1.36

P=2.38 W