Embibe Experts Solutions for Chapter: Current Electricity, Exercise 1: cbse-2018

Define the term ‘conductivity’ of a metallic wire. Write its SI unit.

Using the concept of free electrons in a conductor, derive the expression for the conductivity of a wire in terms of number density and relaxation time. Hence, obtain the relation between current density and the applied electric field $E$.

Using Kirchhoff$\text{'}$s rules, calculate the current through the $40 \mathrm{\Omega }$ and $20 \mathrm{\Omega }$ resistors in the following circuit$:$

What is end error in a metre bridge? How is it overcome? The resistances in the two arms of the metre bridge are $\mathrm{R}=5 \mathrm{\Omega }$ and $\mathrm{S}$ respectively. 

When the resistance $\mathrm{S}$ is shunted with an equal resistance, the new balance length found to be $1.5{\mathrm{l}}_1$, where ${\mathrm{l}}_1$ is the initial balancing length. Calculate the value of $\mathrm{S}$.

A potentiometer can measure emf of a cell because :

Two resistors $R_1$and $R_2$ of $4\Omega$ and $6\Omega$  are connected in parallel across a battery. The ratio of power dissipated in them, P1 : P2 will be

Explain the principle of working of a meter bridge. Draw the circuit diagram for determination of an unknown resistance using it.

In case two cells are identical, each of emf $E=5 \mathrm{V}$ and internal resistance $r=2 \Omega$, calculate the voltage across the external resistance $R=10 \Omega$