How can a megaphone used by a cheerleader allow people on the opposite side of a field to hear her better? a) the metal or plastic of the megaphone cannot absorb the sound waves. b) the inside of the megaphone is like a vacuum because its shape eliminates air pressure. c) the air pressure is greater inside the air pressure than outside and the sound waves are able to travel further. d) solid objects can change the direction of sound waves; megaphones allow users to determine the general direction of the sound.

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: