Electricity and Magnetism Answers

Two positive charges q1 and q2 are separated by a distance r. The charges repel each other with a force F. If the magnitude of each charge is doubled and the distance stays unchanged, what is the new force between the charges?

A point charge q1 is held stationary at the origin. A second charge q2 is placed at point a, and the electric potential energy of the pair of charges is 5.4 x 10^-8J. When the second charge is moved to point b, the electric force on the charge does -1.9x10^-8J of work. What is the electric potential energy of the pair of charges when the second charge is at point b?

How strong / what size N52 Neodymium magnet would you need to work through 5cm of wood (non-student D&T Project trying to make a door lock, but I'm no physicist and am struggling to work this one out, so any help very appreciated!)

A rarefaction and an adjacent compression of a sound wave travelling in air are separated by a distance of 15cm. If the velocity of sound in Air is 330 m/s, What is the frequency?

The user's question is: a 2.5 gram ping pong ball at rest is set in motion by the use of 1.8 J of energy. if all the energy goes into the motion of the ball, what is the balls maximum speed?
I have an answer of 36 or 38 but I don't know how it was derived (detail)

The relative permittivity of a dielectric is 2.25. (a) What is its permittivity? (b) What will be the capacitance if this dielectric is inserted into a 7.8 uF air capacitor?

A coil of 60 turns is wound around an iron ring of ur=1000 having a 20cm diameter and a 10cm2 cross section. The ring contains an air gap of length t=0.1mm. Сalculate the force acting between the pole pieces of the iron ring when the current is 1A.

A plane 1Ghz wave travelling in the air with peak E field of 1v/m is incident normally on a large copper sheet. Find the average power absorbed by the sheet per meter square of the area.

An electron starting from rest moves Unimpeded in an electric field of intensity E volts per meter, find
1. The force it experiences
2. The acceleration
3. The kinetic energy attained in moving through a P.D of v volt
4. The velocity attained in moving through P.D of V volts

How current flow depends on surface area?