Physics Answers

How does the strength of the magnetic field that is 1 cm from a current-carrying 

       wire compare with the strength of the magnetic field that is 4 cm from the wire?

At what distance a long, straight wire carrying a current of 3 A can develop a

        magnetic field of 7x10-7 T

 Find the current in a long, straight wire needed to develop a magnetic field of    

       5x10-7 T at 6m from the wire.

Find the magnetic field at a distance 3m from a long, straight wire carrying a

      current of 2 A.

A woman weighing 75 kg stands on a spring scale in elevator. During the first 3 seconds of motion from rest, the tension T in the hoisting cable is 8300 N. The total mass of the elevator , woman scale is 750 kg.

1.Find the vertical acceleration of the elevator.

2.Find the reading R of the scale in Newtons during this interval.

3.Find the upward velocity of the elevator at the end of a 3 seconds.

A solid copper sphere has a net positive charge. The charge is distributed uniformly over the surface of the sphere, and the electric field inside the sphere is zero. Then a negative point charge outside the sphere is brought close to the surface of the sphere. Is all the net charge on the sphere still on its surface? If so, is this charge still distributed uniformly over the surface? If it is not uniform, how is it distributed? Is the electric field inside the sphere still zero? In each case justify your answers.

A certain region of space bounded by an imaginary closed surface contains no charge. Is the electric field always zero everywhere on the surface? If not, under what circumstances is it zero on the surface?

The voltage across a 10 μF capacitor to charge it with 10 mC is

The air temperature and the velocity of the air have different values at different places in the earth’s atmosphere. Is the air velocity a vector field? Why or why not? Is the air temperature a vector field? Again, why or why not? 

Two identical metal objects are mounted on insulating stands. Describe how you could place charges of opposite sign but exactly equal magnitude on the two objects.