Question

in this b) part how come U dimension come ML^2T^-2?? and here what is U?

Answer 1

As mentioned in the Question, U stands for Energy ( Here, Electrical Energy )

Since, Work Done is also a form of energy ( because It's unit is Joules , which is same as of energy )

So,

Work Done = Force × Displacement

Dimensions of:

Force = MLT^-2

Displacement = L

So,

Dimension of Energy:

==> MLT^-2 × L

==> ML^2T^-2

Hence, Dimension of U ( energy ) is $\sf \bold{ ML^{2}T^{-2} }$