Chapter 12

Two wires of equal lengths, equal diameters and having resistivities ${\rho }_1$ and ${\rho }_2$ are connected in series The equivalent resistivity of the combination is.... (A) $({\rho }_1+{\rho }_2)$ (B) $(1/2)({\rho }_1+{\rho }_2)$ (C) $\text{Missing left or extra right}$ (D) $\sqrt{(}{\rho }_1{\rho }_2)$

Figure, shows a network of eight resistors numbered 1 To 8 , each equal to $2\mathrm{\Omega }$, connected to a $3\mathrm{V}$ battery of negligible internal resistance The current $\mathrm{I}$ in the circuit is .... (A) $0.25\mathrm{A}$ (B) $0.5\mathrm{A}$ (C) $0.75\mathrm{A}$ (D) $1.0\mathrm{A}$

Figure, shows a network of seven resistors number 1 to 7, each equal to $1\mathrm{\Omega }$ connection to a $4\mathrm{V}$ battery of negligible internal resistance The current I in the circuit is.... (A) $0.5\mathrm{A}$ (B) $1.5\mathrm{A}$ (C) $2.0\mathrm{A}$ (D) $3.5\mathrm{A}$

The effective resistance of a n number of resistors connected in parallel in $\mathrm{x}\mathrm{ohm}$. When one of the resistors is removed, the effective resistance becomes y ohm. The resistance of the resistor that is removed is.... (A) $(\mathrm{xy})/(\mathrm{x}+\mathrm{y})$ (B) $(\mathrm{xy})/(\mathrm{y}-\mathrm{x})$ (C) $(\mathrm{y}-\mathrm{x})$ (D) $\sqrt{xy}$

The potential difference through the $3\mathrm{\Omega }$ resistor shown in fig is.... (A) Zero (B) $1\mathrm{V}$ (C) $3.5\mathrm{V}$ (D) $7\mathrm{V}$

when a cell is connected to a resistance $R_1$ the rate at which heat is generated in it is the same as when the cell is connected to a resistance ${\mathrm{R}}_2(<{\mathrm{R}}_1)$ the internal resistance of the cell is.... (A) $(R_1-R_2)$ (B) $(1/2)({\mathrm{R}}_1-{\mathrm{R}}_2)$ (C) \(\left\{\left(\mathrm{R}_{1} \mathrm{R}_{2}\right) /\left(\mathrm{R}_{1}+\mathrm{R}_{2}\right)\right.\) (D) ${\sqrt{R}}_1{R}_2$

Length of a wire of resistance $R\mathrm{\Omega }$ is increased to 10 times, so its resistance becomes $1000\mathrm{\Omega }$, therefore $R=\dots .$ (The volume of the wire remains same during increase in length) (A) $0.01\mathrm{\Omega }$ (B) $0.1\mathrm{\Omega }$ (C) $1\mathrm{\Omega }$ (D) $10\mathrm{\Omega }$

On applying an electric field of $5\times {10}^{-8}{\mathrm{Vm}}^{-1}$ across a conductor, current density through it is $2.5{\mathrm{Am}}^{-2}$ The resistivity of the conductor is $\dots .$ (A) $1\times {10}^{-8}\mathrm{\Omega }\mathrm{m}$ (B) $2\times {10}^{-8}\mathrm{\Omega }\mathrm{m}$ (C) $0.5\times {10}^{-8}\mathrm{\Omega }\mathrm{m}$ (D) $12.5\times {10}^{-8}\mathrm{\Omega }\mathrm{m}$

A wire in a circular shape has $10\mathrm{\Omega }$ resistance. The resistance per one meter is $1\mathrm{\Omega }$ The resultant between $A\mathrm{\&}B$ is equal to $2.4\mathrm{\Omega }$, then the length of the chord $\mathrm{AB}$ will be equal to (A) $2.4$ (B) 4 (C) $4.8$ (D) 6

The network is made of uniform wire. The resistance of portion EL is $2\mathrm{\Omega }$. Find the resistance of star between points $F\mathrm{\&}C.$ (A) $0.985\mathrm{\Omega }$ (B) $1.25\mathrm{\Omega }$ (C) $1.946\mathrm{\Omega }$ (D) $1.485\mathrm{\Omega }$