Why are protons neutrons and electrons called subatomic particles

They are atoms that make up a subatomic particle

Explanation:

Atoms are made up of protons, neutrons and electrons, also known as subatomic particles. Because an atom is neutral, the number of electrons is equal to the number of protons. Electrons circle the nucleus, which is made up of protons and neutrons.

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current