The tiny ball at the end of the thread shown in figure has a mass of $0.5 \, g$ and is placed in a horizontal electric field of intensity $500\, N/C$. It is in equilibrium in the position shown. The magnitude and sign of the charge on the ball is .....$\mu C$
$+ 5.7$
$- 5.7$
$+ 17$
$- 17$
An oil drop of radius $2\, mm$ with a density $3\, g$ $cm ^{-3}$ is held stationary under a constant electric field $3.55 \times 10^{5}\, V\, m ^{-1}$ in the Millikan's oil drop experiment. What is the number of excess electrons that the oil drop will possess ? (consider $\left. g =9.81\, m / s ^{2}\right)$
The electric field in a region is radially outward and at a point is given by $E=250 \,r V / m$ (where $r$ is the distance of the point from origin). Calculate the charge contained in a sphere of radius $20 \,cm$ centred at the origin ......... $C$
Two charges $e$ and $3 e$ are placed at a distance $r$. The distance of the point where the electric field intensity will be zero is .........
Charges $q$, $2q$, $3q$ and $4q$ are placed at the corners $A$,$ B$,$ C$ and $D$ of a square as shown in the following figure. The direction of electric field at the centre of the square is along
How many electrons should be removed from a coin of mas $1.6 \,g$, so that it may float in an electric field of intensity $10^9 \,N / C$ directed upward?