So we want to know what will happen to the needle of a compass that is held upright and pointing left in front of the solenoid if the current in the solenoid is reversed. If the current is reversed in the solenoid then the direction of the magnetic field of the solenoid is also reversed. So the needle that was pointing left will now point right after the direction of the current is changed.
Answer: ![1361.11\ N/C,\text{upward}](https://tex.z-dn.net/?f=1361.11%5C%20N%2FC%2C%5Ctext%7Bupward%7D)
Explanation:
Given
Mass of particle is ![m=2.5\ gm](https://tex.z-dn.net/?f=m%3D2.5%5C%20gm)
Charge of particle is ![q=18\ \mu C](https://tex.z-dn.net/?f=q%3D18%5C%20%5Cmu%20C)
Electrostatic force must balance the weight of the particle
![\lim_{n \to \infty} a_n \Rightarrow mg=qE\\\\\Rightarrow E=\dfrac{2.5\times 9.8\times 10^{-3}}{18\times 10^{-6}}\\\\\Rightarrow E=1361.1\ N/C](https://tex.z-dn.net/?f=%5Clim_%7Bn%20%5Cto%20%5Cinfty%7D%20a_n%20%5CRightarrow%20mg%3DqE%5C%5C%5C%5C%5CRightarrow%20E%3D%5Cdfrac%7B2.5%5Ctimes%209.8%5Ctimes%2010%5E%7B-3%7D%7D%7B18%5Ctimes%2010%5E%7B-6%7D%7D%5C%5C%5C%5C%5CRightarrow%20E%3D1361.1%5C%20N%2FC)
Direction of the electric field is in upward direction such that it opposes the gravity force.
It would mostly depend on its weight
initial velocity = 0 = v₍i₎
final velocity = ? = v₍f₎
t = 12 sec
Acceleration = 4m/s²
First we have to find the distance d, for this we use the
formula,
D = v₍i₎t + 1/2at²
D = 0(12) + ½ (4)(12)²
Distance = d = 288 m
Now to find the Vf use the formula,
V₍f₎² = v₍i₎² + 2ad
V₍f₎² = (0)2 + 2(4)(288)
V₍f₎² = 2304
V₍f₎ = 48 m/s
so the velocity at the end of 12 sec is 48 m/s