Equations 22-8 and 22-9 are approximations of the magnitude of the electric field of an electric dipole, at points along the dipole axis. consider a point p on that axis at distance z = 3.00d from the dipole center(where d is the separation distance between the particles of the dipole). let eappr be the magnitude of the field at point p as approximated by equations 22-8 and 22-9. let eact be the actual magnitude. by how much is the ratio eappr/eact less than 1?

On axis of the dipole the electric field is given by

now if we approximate above equation

now we will find the ratio of these two

put r = 3d

so above is the ratio of two field

given data:

determine the horse power (h.p) = ?

force applied to move the box(f) = 10 pounds,

box lifted from a distance         (d) = 3 feet

time taken to lift                         (t) = 10 sec,

the horse power is defined as amount of work required to move a load. the horse power is equal to 550 foot-pound per second

                  1 h.p   = 550 foot-pound/second

it can also be defined as the the load that need to be move a body for certain distance in a certain amount of time.

mathematically,

                      h.p = (force × distance)/ time

                            = (10 × 3)/ 10

                            = 30/10

                            = 3 foot -pound/sec

hence, the horse power is needed to move the box is 3 foot-pound/second

important note: 1 h.p = 550 foot-pound/second = 746 watts

it has to be b, about 97 percent.