Two wires $A$ and $B$ of the same material have lengths $L_A, L_B$ and radii $R_A, R_B$ and drift velocities $v_A, v_B$ respectively. Both wires carry the same current. If $L_A = L_B$ and $R_A = 2R_B$,then the value of $\left(\frac{v_A}{v_B}\right)$ is:

Drift speed of electrons,when $1.5 \, A$ of current flows in a copper wire of cross-section $5 \, mm^2$,is $v$. If the electron density in copper is $9 \times 10^{28} \, m^{-3}$,the value of $v$ in $mm/s$ is close to (Take charge of electron to be $1.6 \times 10^{-19} \, C$).

$A$ current $I$ flows through a uniform wire of diameter $d$,when the mean drift velocity is $v_d$. The same current will flow through a wire of diameter $d/2$ made of the same material,if the mean drift velocity of the electrons is

In a metal, the charge carrier density is $9.1 \times 10^{28} \,m^{-3}$ and its electrical conductivity is $6.4 \times 10^7 \,S \,m^{-1}$. When an electric field of $10 \,N C^{-1}$ is applied to the metal, then the average time between two successive collisions of electrons in the metal is (Mass of electron $= 9.1 \times 10^{-31} \,kg$; charge of electron $= 1.6 \times 10^{-19} \,C$)

$A$ copper wire of length $1\, m$ and radius $1\, mm$ is joined in series with an iron wire of length $2\, m$ and radius $3\, mm$ and a current is passed through the wires. The ratio of the current density in the copper and iron wires is

The number density of free electrons in copper is nearly $8 \times 10^{28} \ m^{-3}$. $A$ copper wire has an area of cross-section $= 2 \times 10^{-6} \ m^2$ and is carrying a current of $3.2 \ A$. The drift speed of the electrons is $..... \times 10^{-6} \ m \ s^{-1}$.