Griffiths 2.31 Electrostatics

Griffiths problem 2.31, work and energy in electrostatics. Configuration of charges.

The intensity of sunlight at the top of the Earth’s atmosphere is about 1390 W/m2. The distance between the Sun and the Earth is 1.50×1011m, whle that between the Sun and Mars is 2.28 ×1011m. What is the intensity of sunlight at the surface of Mars?

The intensity of sunlight at the top of the Earth’s atmosphere is about 1390 W/m2. The distance between the Sun and the Earth is 1.50×1011m, whle that between the Sun and Mars is 2.28 ×1011m. What is the intensity of sunlight at the surface of Mars?

Coulomb's Law

I am trying to figure out the charge q on two seperate but equal in magnitude spheres with the same mass, m. The question is as follows: 2 small speres with mass m = 15.1 g are hung by silk threads of length L = 1.21 m from a common point. When the speres are given equal charges, so that q_1 = q_2 = q, each thread hangs at an angle theta = 26 degrees from the vertical. Find the magnitude q. It says to use 9.81 m/s^2 as the acceleration due to gravity and 8.85 * 10^-12 C^2/Nm^2 as the permittivity of free space. I'm having problems because there are two unknowns. I can figure out the force due to gravity on the spheres and the distance between them. But I cannot figure out the... click for more

Electric Potential and Electric field

(See attached file for full problem description with diagram) (1) Two point charges, Q1 = +2 x 10-6 C and Q2 = -3 x 10-6 C, are situated as shown. (Refer to the attached file to view the diagram) (a) Find the electric potential at point A and at point B. (b) Find the work needed to move a point charge Q3 = 5 x 10-6 C from point A to point B along the curved path shown by the solid line (2) A solid, insulating sphere of radius a has a uniform charge density ρ and a total charge +Q. Find the magnitude of the electric field in the regions ra . Draw the schematic graph of electric field (E vs. r).

EMF induced by train's axles

An engineer plans to light a train by utilizing the emf induced in the axles of the train running on the tracks. a. If the downward component of the earth’s magnetic field is 0.6 X 10^-4 T, and the tracks are 1.5m apart, how large is the emf produced between the tracks by a train traveling at 40 m/s? b. Could this voltage be utilized on the moving train? The answer is Yes, but how c. Could the voltage be utilized at a train station at the distant end of the tracks? I would think Yes again, but how?