B - the voltage drop is 60 V
Answer:
The magnitude of the frictional force is 
Explanation:
From the question we are told that
The force exerted on the box is 
Generally for the box to remain at rest then it means that the frictional force is greater than or equal to the force applied to move it i.e

=> 
Answer:
The magnetic field is 
Explanation:
From the question we are told that
The inner radius is 
The outer radius is 
The distance from the axis of the conductor is 
The current carried by the conductor is 
According to Ampere's circuital law , the magnetic field at a point that is
from the axis of the conductor
![B = \frac{\mu_oI}{2 \pi d } [\frac{d - r_1}{r_2 -r_1} ]](https://tex.z-dn.net/?f=B%20%3D%20%20%5Cfrac%7B%5Cmu_oI%7D%7B2%20%5Cpi%20d%20%7D%20%5B%5Cfrac%7Bd%20-%20r_1%7D%7Br_2%20-r_1%7D%20%5D)
Where
is the permeability of free space with a value of
substituting values
![B = \frac{(4 \pi *10^{-7})(80)}{2 * 3.142 * 2 *10^{=3} } [\frac{(2^2 - 1 ^2 )*10^{-3}}{(3^2 - 1^2) *10^{-3}} ]](https://tex.z-dn.net/?f=B%20%3D%20%20%5Cfrac%7B%284%20%5Cpi%20%2A10%5E%7B-7%7D%29%2880%29%7D%7B2%20%2A%203.142%20%2A%202%20%2A10%5E%7B%3D3%7D%20%7D%20%5B%5Cfrac%7B%282%5E2%20-%201%20%5E2%20%29%2A10%5E%7B-3%7D%7D%7B%283%5E2%20-%201%5E2%29%20%2A10%5E%7B-3%7D%7D%20%5D)
