If opposite poles repel each other,
why does the north end of a compass point to
the North Pole? Explain your reasoning.

The earth's magnetic field causes a compass to point north, (cuz as we know)  compasses are powered by magnets. The magnets inside compasses are drawn to the magnetic North Pole, which is about 1,000 miles south of the actual North Pole. Therefore, even though a compass always points north, it does not always point toward the true north.

Explanation:

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 duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.