Multiple Choice: 4) In which of these cases is positive work being done on the person?
a) The person leans against a wall
b) The person rides on a car around a roundabout at constant speed
c) The person jumps out of an airplane and falls downwards
d) The person pushes a lawnmower around a yard

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation:

the entire statement is true and correct.  

there's no diagram, nothing is illustrated, and no question is asked.

i would say