Class 12 NEET Physics Current Electricity Questions Part 1

Let ρ and A be resistivity and area of cross-section of the wire respectively.
The wire is bent in the form of right triangle as shown in figure.
\Resistance of side AB is R1=

3ρ

A

Resistance of side BC is R2=

4ρ

A

Resistance of side AC is R3=

5ρ

A

∴ The resistance between the ends A and B is
RAB=

R1(R2+R3)

R1+R2+R3

=

3ρ A ( 4ρ A + 5ρ A )

3ρ A +( 4ρ A + 5ρ A )

=

27

12

ρ

A

The resistance between the ends B and C is
RBC=

R2(R1+R3)

R2+R1+R3

=

4ρ A ( 3ρ A + 5ρ A )

4ρ A + 3ρ A + 5ρ A

=

32

12

ρ

A

The resistance between the ends A and C is
RAC=

R3(R1+R2)

R3+R1+R2

=

5ρ A ( 3ρ A + 4ρ A )

5ρ A + 3ρ A + 4ρ A

=

35

12

ρ

A

∴ RAB:RBC:RAC =

27

12

:

32

12

:

35

12

=27:32:35