A long wire carries a current of 3.0 A along the axis of a long solenoid (radius = 3.0 cm, n = 900 turns/m, current = 30 mA). What is the magnitude of the magnetic field at a point 2.0 cm from the axis of the solenoid? Neglect any end effects.
A) 34 μT
B) 64 μT
C) 30 μT
D) 45 μT
E) 4.0 μT

Question

Quizplus · Accepted Answer

We can use the equation for the magnetic field inside a solenoid:
B = μ*n*I
where μ is the permeability of free space, n is the number of turns per unit length, and I is the current.

Plugging in the given values, we get:
B = (4π×10^-7 T·m/A) * (900 turns/m) * (0.03 A)
B = 0.081 T = 81 mT

To find the magnetic field at a point 2.0 cm from the axis of the solenoid, we can use the formula for the magnetic field of a current-carrying wire:
B = (μ0/4π) * (2I/R)
where R is the distance from the wire and I is the current.

Plugging in the given values, we get:
B = (4π×10^-7 T·m/A) / (4π) * (2*(3 A)) / (0.02 m)
B = 45 μT

Therefore, the answer is D.

A Long Wire Carries a Current of 3