Sound is generated by the speaker cone vibrating in different ways. The cone vibrates as different magnetic forces act on the current-carrying coil. Why do the magnetic forces acting on the coil change as the current running through the coil changes?
A.
because the current causes the magnet to lose power
B.
because coils of wire are not usually attracted to magnets
C.
because the current causes the magnet to gain power
D.
because the current generates a magnetic field around the coil

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:

a coal burning power plant

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