BDS Learning Application (RS)

  Electric Charges and Fields      Problems Question1.A charged spherical conductor has a surface density of 0.7 Cm -2 . When its change is increased by 0.44 C, the charge density changes by 0.14 Cm -2 . Find the radius of the sphere and initial charge on it.   Solution. The spherical charged conductor has surface density Question4. A charge is distributed uniformly over a ring of radius ‘a’. Obtain an expression for the electric intensity ‘E’ at a point on the axis of the ring. Hence show that for the points at a large distance from the ring, it behaves like a point charge.   Solution. Suppose that the ring is placed with its plane perpendicular to the x-axis. Consider a small element dl of the ring. As the total charge q is uniformly distributed, the charge dq on the element dl is   Question5. A thin semicircular ring of radius ‘a’ is charged uniformly and the charge per unit length is ‘λ’. Find the electric field at its c

Electric Charges and Fields     Problems Question1. The charged particle, of charge 2 μ C and mass 10 milligrams, moving with a velocity of 1000 m / s entres a uniform electric field of strength 10 3 NC -1 directed perpendicular to its direction of motion. Find the velocity and displacement, of the particle after 10 s. Solution. The velocity of the particle, normal to the direction of the field.                   V x = 1000 ms -1 ,       is constant The velocity of the particle, along the direction of the field, after 10 s is given by Question2. Assuming that the charge on an atom is distributed uniformly in a sphere of radius 10 -10 m, what will be the electric field at the surface of the gold atom? For gold, Z = 79. Solution. The charge may be assumed to be concentrated at the center of the sphere of radius 10 -10 m.                                              r = 10 -10 m,                                      

  Electric Charges and Fields      Problems Question1. Three-point charges of +2 μC, -3 μC, and -3 μC are kept at the vertices A, B, and C respectively of an equilateral triangle of the side of 20 cm as shown in the figure (a). What should be the sign and magnitude of the charge to be placed at the mid-point (M) of side BC so that the charge at A remains in equilibrium? Question2. Calculate the electric field strength required to just support a water drop of mass 10 -3 kg and having a charge of 1.6 × 10 -19 C. Solution. Here m = 10 -3 kg, q = 1.6 × 10 -19 C Let E be the strength of the electric field required to just support the water drop. Then Force on water drop due to electric field = Weight of water drop Or                                    qE = mg Question3. Calculate the voltage needed to balance an oil drop carrying 10 electrons when located between the plates of a capacitor which are 5 mm apart. The mass of oil drop is 3 × 10 -16 kg. Take g = 10 ms -2 . Question4.