Which particles contribute to the atomic number and why ??

the number of protons in the nucleus that are found in an atom is what determines an element's atomic number.why you may ask and thats because Protons contribute to the mass of an atom.(along with neutrons but they dont have a charge)but protons provide a positive charge to the nucleus.  

Explanation:

because the atom is electrically neutral, the number of electrons must equal the number of protons.

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