I'll give brainliest! During the last 5 million years, how often have the poles reversed
themselves?
5
20
10
15

Earth's magnetic field has flipped its polarity many times over the ... Earth has settled in the last 20 million years into a pattern of a pole reversal about ... And while reversals have happened more frequently in "recent" years, when ... per year, as opposed to about 10 miles per year in the early 20th century.

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:

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle