Can I apply H4 visa while I am holding valid H1 Visa?

[kuldeep.dwh]

I am holding valid H-1B Visa but has not traveled to US.
My wife is already working in US on H-1B Visa.

Can I apply for H4 visa on my wife's H-1B visa without affecting my H-1B Visa?
If Yes, Can I travel to US on H4 visa and after sometime I can work in US with my present employer on my H-1B.

Thanks in advance.