Calculate the resistivity of the material of a wire of length 1 cm, radius 0.07 m and of resistance 20 ohms.
A. 30.8 ohm-m
B. 36.0 ohm-m
C. 0.31 ohm-m
D. 39.0 ohm-m
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Answer:
Correct option is
B
2.514×10
−7
Ωm
Given : R=2Ω l=1 m d=0.4 mm =0.0004 m
Cross section area of wire A=
4
πd
2
=
4
π×(0.0004)
2
=1.256×10
−7
m
2
Resistivity of the material ρ=
l
RA
∴ ρ=
1
2×1.256×10
−7
=2.514×10
−7
Ωm
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