A wire of resistance 20 ohm is drawn out so that its thrice its original length. Calculate its new resistance & resistivity.
Answers
Answered by
1
Answer:
assuming the wire is cylindrical, and of uniform cross section area A,
initial lenght = l ; new length = L =3l
original volume= new volume.
3.14r2l = 3.14r'2L
3.14r2l = 3.14r'23l
A.l = A'.3l
A'= A/3
R (resistance) = p.l/A (p = resistivity)
R' = p. L/A' = p. 3l/ A'
R' = p. 6l/A
R' = 6( p.l/A)
R' = 6R
therefore , new resistance R' = 6 x 20 = 120 ohm
Similar questions