The density of copper is $9\,\, imes \,\,{10^3}\,\,{\rm{kg}}/{{\rm{m}}^3}$ and its atomic mass is ${\rm{63}}{\rm{.5}}\,\,{\rm{u}}$. Each copper atom provides one free electron. Estimate the number of free electrons per cubic metre in copper.

The steady current flows in a metallic conductor of non-uniform cross-section. The ${\rm{quantity}}\,\,{\rm{/}}\,{\rm{quantities}}$ constant along the length of the conductor ${\rm{is}}\,\,{\rm{/}}\,\,{\rm{are}}$

In hydrogen atom, the electron makes $6.6\,\, imes \,\,{10^{15}}$ revolutions per second around the nucleus in an orbit of radius $0.5\,\, imes \,\,{10^{ - 10}}\,\,m$. It is equivalent to a current nearly

The current in a conductor varies with time $t$ as $I = 2t + \,\,3{t^2}$ where $I$ is in ampere and $t$ in seconds. Electric charge flowing through a section of the conductor during $t = 2\,\,\sec$ to $t = 3\,\,\sec$ is

The current flowing in a copper voltmeter is ${\rm{1}}{\rm{.6}}\,\,{\rm{A}}$. The number of $C{u^{ + + }}$ ions deposited at the cathode per minute are

The electron in a hydrogen atom circles around the proton in $1.5941\,\, imes \,\,{10^{ - 18}}$. The equivalent current due to motion of the electrons is

Ampere hour is the unit of

There is a current of \begin{array}{*{20}{l}} {{\rm{0}}{\rm{.21}}\,\,{\rm{A}}} \end{array} in a copper wire whose area of cross-section is ${10^{ - 6}}\,{{\rm{m}}^2}$. If the number of free electrons per ${{\rm{m}}^3}$ is $8.4\,\, imes \,{10^{28}}$, then find the drift velocity,$\left( {e = 1.6\,\, imes \,\,{{10}^{ - 19}}\,\,{\rm{C}}} \right)$

Consider a conductor with a non-uniform cross-sectional area. If a steady current flows through it, which of the following quantities remains constant along the length of the conductor?

When a current flows through a conductor its temperature

In cosmic rays ${\rm{0}}{\rm{.15}}$ protons ${\rm{c}}{{\rm{m}}^{ - 2}}\,\,{\sec ^{ - 1}}$⁡ are entering the earth’s atmosphere. If the radius of the earth is ${\rm{6400}}\,{\rm{ km}}$, the current received by the earth in the form of cosmic rays is nearly.