Method to determine the surface temp of sun

Briefly describe the method to determine the surface temp of sun

Finding the equation of motion in a magnetic field where a conductor rolls over two parallel infinite wires.

The conductor bridge is giving an initial velocity V0 to the right. The circuit completed by this bridge has an increasing area as the bridge moves to the right which means an increasing magnetic flux. Thus we know from Faraday's law that a current is created in the circuit completed by this bridge proportional to its velocity. So if the bridge continues to move freely forever, we have an infinite source of energy through generation of current. How is this violation of energy conservation resolved? Find the equation of motion of the bridge and show that it slows down to rest eventually.

Electric field strength

To an observer very close to a spherical surface charge distribution, the sphere's surface looks flat and stretches essentially to the horizon in all directions. It will therefore look to the observer as if it were an infinite flat charged sheet. Argue that if the observers distance d from the spherical surface is very small compared to the sphere's radius R, the electric field strength for a uniformly distributed spherical surface charge is the same as that for an infinite sheet

Electric field vectors

Consider two circular parallel plates of radius R separated by a distance d  R. Assume that these plates have uniformly distributed surface charges of Q and -Q. Electric field vectors in the region between the plates will all point perpendicular to the plates from the positive plate to the negative plate and will have a magnitude of 4k (see attachment)

neutral metal spheres

Imagine that you have two identical neutral metal spheres on insulating stands and a charged rubber rod. Using diagrams, carefully describe a step-by-step process that uses the rod to give the two spheres exactly opposite charges(all without touching either sphere with the rod)Take care to construct your procedure so that it ensures that the charges on each sphere will be exactly equal in magnitude, not just approximately equal.