CBSE Class 12science Physics Electric Charges and Fields
 an infinite line charge produces a field of 9×10^4 N/C at a distance of 2 cm calculate the linear charge
 Three charges \( 1 \mathrm{C},1 \mathrm{C} \), and \( 2 \mathrm{C} \) are kept on \( X \) axis \( 5 \mathrm{~cm}, x=0 \mathrm{~cm} \) amd \( x=10 \mathrm{~cm} \) respectively find net force one each of them
 ln a Millikan’s oil drop experiment, the horizontal plates are 1.5 cm apart. With the electric field switch off an oil drop is observed to fall with a steady velocity of 2.5×10^{2} cm s^{1}. When the field is switched on the upper plate being positive, the drop just remains stationary when the p.d. between the plates is 1500 V. Calculate the radius of drop (b) How many electronic charges does it carry? (c)If the p.d. between the two plates remains unchanged, with what velocity will the drop move when it has collected two more as a result of exposure to ionising radiation? (Oil density, rho=900 kgm^{3} , Viscosity of air, eta =1.8×10^{5} Nsm^{2}, Density of air, σ=1.293 kg m^{3})
 A beam of electrons, moving with avelocity of 10^7m/s, enters midway between two horizontal parallel plates in a directions parallel to the plates. Each plate is 5 cm long. These plates are kept 2 cm apart and a potential difference of 90 V is applied between, them. Calculate the velocity of the electron beam with which it just grazes the edge of the positive plate. (e /m=1.8×10^{11} c/kg)
 An oil drop of mass 3.25*10^(15) kg falls vertically with uniform velocity , through the air between vertical parallel plates which are 2 m apart. When a p.d. of 1000 V is applied to the plates the drop moves to the positively charged plate , being inclined at 45 degrees to the vertical. Calculate the charge on the drop.
 Two point charges 2 C and 3 uC are placed at two comers of an equilateral triangle of side 20 cm in free space. Calculate the magnitude of resultant electric field at the third corner of the triangle. If an &  particle is placed at the third corner, what is the force acting on it? (Charge on & – particle is 3.2 x 1019 €).
 State Gauss's theorem ? Derive the expression for electric field due Spherical hollow conductor and infinitely charged sheet and linearly charged conductors.

A simple pendulum is having bob of mass m carrying a charge q and is hanging from ceiling. A uniform electric field E is applied in downward direction then time period of simple pendulum is.

An electric field E is applied between the plates a and b as shown in the figure a charge particle of mass m and charge q is projected along the direction as shown fig it's velocity v find vertical distance y covered by the partical when goes out of the electric field region