A beam contains $2 \times 10^8$ doubly charged positive ions per cubic centimeter, all of which are moving with a speed of $10^5 \,m/s$. The current density is ............. $A/m^2$
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An electric bulb rated as $200\, {W}$ at $100 \,{V}$ is used in a circuit having $200\, {V}$ supply. The resistance $'R'$ that must be put in series with the bulb so that the bulb delivers the same power is $.....\,\Omega$
In a potentiometer arrangement, a cell of $emf$ $1.25\,V$ gives a balance point at $35.0\,cm$ length of the wire. If the cell is replaced by another cell and the balance point shifts to $63.0\,cm,$ the $emf$ of the second cell ............... $V$
A copper wire of length $10\,m$ and radius $\left(10^{-2} / \sqrt{\pi}\right) m$ has electrical resistance of $10 \,\Omega$. The current density in the wire for an electric field strength of $10( V / m )$ is :
A uniform wire of resistance $9\, ohm$ is bent in the form of a circle. The effective resistance across the points $A$ and $B$ is ............... $\Omega$
The following circuit consist of a $5 \,\mu F$ capacitor, having charge $50 \,\mu C$ as shown. The switch is closed at $t=0$. The value of current in $2 \,M \Omega$ resistor at $t=0$ is ........... $\mu A$