[jQuery] jQuery.noConflict() is not working

[Bluesapphire]

Hi!
    I am using following things in separate JS file:

a-
    var dom = {};
    dom.query = jQuery.noConflict(true);

b-
   var jQ = jQuery.noConflict();

c-
      jQuery.noConflict();

Neither of above work and Firbug gives error.

But $ works perfectly.

Can some one guide me where I am doing mistake.

Thanks in advance