What shape can be drawn through a solenoid to determine the magnitude of its magnetic field?

 Rectangular shape

Explanation: we consider a rectangular shape when we find the magnitude of the magnetic field.

We apply Ampere's circuital law to a rectangular loop.

According to Ampere's circuital law, the magnetic field of a solenoid is directly proportional to the product of the current which is flowing around the solenoid and number of turns per unit line of the solenoid.

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