Question

PRACTICE IT Use the worked example above to help you solve this problem. (a) Calculate the resistance per unit length of a 44 gauge nichrome wire of radius 0.642 mm. 12/m (b) If a potential difference of 10.7 V is maintained across a 1.00 m length of wire, what is the current in the wire? (c) The wire is melted down and recast with triple its original length. Find the new resistance RN as a multiple of the old resistance Ro- Ro EXERCISE HINTS: GETTING STARTED I I'M STUCK! What is the resistance of a 6.4 m length of nichrome wire that has a radius of 0.321 mm? How much current does It carry when connected to a 120 V source? RE 22 Need Help? Read It

Answer 1

Resistivity of nichrom wird radius of wire e=1.6x15 brom r = 0.642mm = 0.642X103m A = 782 - T (0.642 A = 1.294x106m2 Area of wire → Resistance Ph unit = 1.6410-6 1.294x10-6. los (le) = 1.24 del 1 V = 10.7 current I = , e- lm > R=1.24 u 1 = 10.7 n. 1.27 = 8.62 A I= 8.62 AT (c) di d, da-3d A A A A Volume = - AXI Ax3d v=AXI so knew = Q3 1 – x3 ed ALB I knew - 9R

- l = 6.4m A = ły2 e = 1.68106 rom (nichrome) - (ο. 21x / 3 ) 2 = 0.323x106m2 A = 0.3 23x156 m2 Resistance R l l = 1.68106 x 6.4. .. 323 x 10 6 ✓ [R = 31.70 d ① I I = = 120 120 31.7.0 = 3.78 A