Q : A wire of 3ohm resistance and 15cm in length is stretched to 45cm length. Calculate (i)new cross sectional area, (ii)new resistance (iii)resistivity. Assume that wire has uniform cross sectional area
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Resistance R=3ohm
length L=15cm=0.15m
R=resistivity L/A
3=rho 0.15/A
rho /A=3/0.15………1
new length L1=45cm=0.45m
The area is same then
New resistance R1 =rho L1/A
R1=3/0.15 x L1
R1=3x0.45/0.15
R1=9 Ohm
OR
Since the volume remains same
Equating the new and old resistances
We get
New resistance =9×old resistance
=27
New area=old area÷3
0.16
Resistivity remains same
I hope so
length L=15cm=0.15m
R=resistivity L/A
3=rho 0.15/A
rho /A=3/0.15………1
new length L1=45cm=0.45m
The area is same then
New resistance R1 =rho L1/A
R1=3/0.15 x L1
R1=3x0.45/0.15
R1=9 Ohm
OR
Since the volume remains same
Equating the new and old resistances
We get
New resistance =9×old resistance
=27
New area=old area÷3
0.16
Resistivity remains same
I hope so
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