Answer:
I = 2172.46 A
Explanation:
Given that,
The length of a solenoid, l = 2.1 m
The inner radius of the solenoid, r = 28 cm = 0.28 m
The number of turns in the wire, N = 1000
The magnetic field in the solenoid, B = 1.3 T
We need to find the current carried by it. We know that, the magnetic field in a solenoid is given by :

Put all the values,

So, it carry current of 2172.46 A.
Answer: yes a quantity have different dimensions in different system of units . No,because in different system of units doesn't change the quantity but it only changes the numerical.
Good luck !
D
Using the kinetic energy 1/2mv^2 formula
5*10^5 is the answer