Question 2 :
A constant potential difference is applied between the ends of the wire. If the length of the wire is <span>elongated $4$ times, then the drift velocity of electrons will be:<br/></span>

Question 3 :
A current I flows through a uniform wire of diameter d when the mean electron drift velocity is<br/>V. The same current will flow through a wire of diameter d/2 made of the same material if the<br/>mean drift velocity of the electron is:<br/>

Question 4 :
A battery of {tex}24{/tex} cells, each of emf {tex} 1.5 V {/tex} and internal resistance {tex} 2 \Omega {/tex} is to be connected in order to send the maximum current through a {tex}12{/tex} {tex} \Omega {/tex} resistor. The correct arrangement of cells will be

Question 5 :
A current of $16 \ A$ is made to pass through a conductor in which the number density of free electrons is $\displaystyle 4\times { 10 }^{ 28 }{ m }^{ -3 }$ and its area of cross section is $\displaystyle { 10 }^{ -5 }{ m }^{ 2 }$. The average drift velocity of free electrons in the conductor is:

Question 6 :
A counter consists of a cylindrical cathode of radius $1 cm$ and an anode wire of radius $0.01 cm$ which is placed along the axis of the cathode. A voltage of $2.3 kV$ is applied between the cathode and anode. The electric field on the anode surface must be :<br/>

Question 7 :
A copper wire of $3\ mm^{2}$ cross sectional area carries a current of $5\ ampere$. The magnitude of the drifty velocity for the electrons in the wire, (Assume copper to be monovalent, $M_{Cu} = 63.5\ kg/k\ mol$ and density of copper $= 8920\ kg/m^{3})$.

Question 8 :
A 1-meter length 22 gauge of copper wire has a current of 1 mA passing through it $1.7\times10^8m$<span class="MathJax"><span class="MJX_Assistive_MathML">=1.7108m</span></span> in this wire.

Question 9 :
An ionization chamber with parallel conducting plates as anode and cathode, has $5\times 10^{7}$ electrons and the same number of singly charged positive ions per $cm^{3}$. The electrons are moving towards the anode with velocity $0.4\ m/s$. The current density from anode to cathode is $4\mu A/m^{2}$. The velocity of positive ions moving towards cathode is

Question 10 :
Find the electric field in the copper wire of area of cross section $2\ mm^2$ carrying a current of $1\ A.$ The resistivity of copper is $1.7\times 10^{-8}\Omega m$.<br>

Question 11 :
A capacitor is charged and battery is disconnected .Now the distance between the plates is increased slightly

Question 12 :
The frequency for which $5\mu F$ capacitor has a reactance of $10,000 \Omega$ is

Question 13 :
Consider a huge charge reservoir at potential $V=200$ volts. A spherical capacitor $C_{1}=40nF$ is brought in contact with the charge reservoir and then removed. Afterwards, another spherical capacitor $C_{2}=30nF$ is brought in contact with $C_{1}$ and removed. This process is repeated many times . Assume that potential of reservoir does not change during this exercise. Then the charge in $\left ( \mu C \right )$ on $C_{2}$ after a very long time is :<br/>

Question 14 :
Capacity of an isolated sphere is increased $n$ times when it is enclosed by an earthed concentric sphere. The ratio of their radii is

Question 15 :
Two metal spheres (radii $r_1, r_2$ with $r_1 &lt; r_2$) are very far apart but are connected by a thin wire. If their combined charge is Q, then what is their common potential?

Question 16 :
A dielectric slab of thickness $6\ cm$<b> </b>is placed between the plates of a parallel plate capacitor. If the distance between the plates is reduced by $4\ cm$, the capacity of the capacitor remains same. Find the dielectric constant of the medium.

Question 17 :
Two plates (area = $5$ ) charged to $ +q_1$ and $+q_2 (q_2 &lt; q_1) $ are brought closer to form a capacitor of capacitance $C$ . The potential difference across the plates is :

Question 18 :
In 1909, Robert Millikan was the first to find the charge of an electron in his now-famous oil-drop experiment. In that experiment, tiny oil drops were sprayed into a uniform electric field between a horizontal pair of oppositely charged plates.The drops were observed with a magnifying eyepiece, and the electric field was adjusted so that the upward force on some negatively charged oil drops was just sufficient to balance the downward force of gravity. That is, when suspended, upward force qE just equaled mg. Millikan accurately measured the charges on many oil drops and found the values to be whole number multiples of $1.6 \times 10^{-19} C$ the charge of the electron. For this, he won the Nobel prize. If a drop of mass $1.08 \times 10^{-14} kg$ remains stationary in an electric field of $1.68 \times 10^5 NC^{-1}$, then the charge of this drop is :<br/>

Question 19 :
The capacitance of two concentric spherical shells of radii $R_{1} \, and \, R_{2} (R_{2} &gt; R_{1})$ is:

Question 20 :
A capacitance is formed by two identical metal plates. The plates are given charges $Q_1$ and $Q_2 (Q_2 &lt; Q_1) $ . If capacitance of the capacitor is $C,$ what is the p.d. between the plates?