Class 12 NEET Physics Current Electricity Questions Part 1

Here, Length of each rod, l=1 m
Area of cross-section of each rod,
A=0.01 cm2=0.01×10−4 m2
Resistivity of copper rod,
ρcu=1.7×10−6Ωcm =1.7×10−6×10−2Ωm
=1.7×10−8Ωm
Resistivity of iron rod,
ρFe=10−5Ωcm =10−5×10−2Ωm=10−7Ωm
∴ Resistance of copper rod,
RCu=ρCu

l

A

and resistance of iron rod,
RFe= ρFe

l

A

As copper and iron rods are connected in series, therefore equivalent resistance is
R=RCu+RFe =ρCu

l

A

+ρFe

l

A

=(ρCu+ρFe)

l

A

Voltage required to produce 1 A current in the rods is
V=IR=(1)(RCu+RFe)
=(ρCu+ρFe)(

l

A

)
=(1.7×10−8+10−7) (

1

0.01×10−4

)V
=10−7(0.17+1)(106)V =1.17×10−1V
=0.117 V