Question

(i) Define ampere in terms of force between two current carrying conductors.
(ii) What is an ideal transformer?

Answer 1

(i) Ampere : One ampere is the current, if it is maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed one meter apart in vacuum, would produce between these conductors a force equal to $2\times {10}^{-7}$ Newton per metre of length.
(ii) Ideal transformer : A transformer which does not have any loss in it, means no core losses, copper losses and any other losses, is called ideal transformer. For ideal transformer $P_{out}=P_{in}$, so efficiency $\eta =100\%$ (But practically, efficiency of transformer lies between $70\%-90\%$) Ideal transformer is a theoretical concept (imaginary transformer), practically it is not possible.