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# Physics HELP!!! watch

1. I was struggles by 4 questions!!! Please Help! It takes me 4 hours and I still cant solve it.

1. A cube with side s has each of its corner placed an identical charge q. Find the magnitude of the electric field at the center of one of the face of the cube.

2. A particle with a charge of −60.0 nC is placed at the center of a non-conducting spherical shell of inner radius 20.0 cm and outer radius 25.0 cm. The spherical shell carries charge with a uniform density of −1.33 µCm^-3. A proton moves in a circular orbit just outside the spherical shell. Calculate the speed of the proton.

3. Three charges of −q, +q, and +q are situated at the corners of a regular triangle with side length s. How much work does it takes to assemble the whole configuration of these charges? Find also the work done required by an external agent to remove the charge of −q. Please indicate clearly the sign of each answer. Absolute values of the quantities will not be accepted.

4. A long, straight wire is surrounded by a cylindrical metal shell whose axis coincides with that of the wire. The wire has a charge per unit length of λ, and the cylinder has a net charge per unit length of 2λ. From this information, use Gauss’s law to find (a) the charge per unit length on the inner surface of the cylinder, (b) the charge per unit length on the outer surface of the cylinder, and (c) the electric field outside the cylinder a distance r from the axis.

2. q.1) Consider one particular face. Show that the electric field due to four identical charges at the corners of this face is zero. They are equal and opposite. Electric field due to rest four charges can be calculated by calculating the distance ( use geometry) of the charge and the center of the face considered. Considering electric field to be a vector and taking care of the directions properly add them vectorially using component method.
3. (Original post by sengupta)
q.1) Consider one particular face. Show that the electric field due to four identical charges at the corners of this face is zero. They are equal and opposite. Electric field due to rest four charges can be calculated by calculating the distance ( use geometry) of the charge and the center of the face considered. Considering electric field to be a vector and taking care of the directions properly add them vectorially using component method.
Thanks man. But how about the other 3 questions

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