NEET Physics Current Electricity Questions Solved

Following figure shows cross-sections through three long conductors of the same length and material, with square cross-section of edge lengths as shown. Conductor B will fit snugly within conductor A, and conductor C will fit snugly within conductor B. Relationship between their end to end resistance is

(1) RA = RB = RC

(2) RA > RB > RC

(3) RA < RB < R

(4) Information is not sufficient

(1) All the conductors have equal lengths. Area of cross-section of A is $\left\{{\left(\sqrt{3}\text{\hspace{0.17em}}a\right)}^{2}-{\left(\sqrt{2}\text{\hspace{0.17em}}a\right)}^{2}\right\}={a}^{2}$

Similarly area of cross-section of B = Area of cross-section of C = a2

Hence according to formula $R=\rho \frac{l}{A};$ resistances of all the conductors are equal i.e. RA = RB = R

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