Because other scientists and science in general rely on their collegues' research which in turn allows development of our knowledge on the given subject. The more dont-to-earth reason may be safety. If someone performs an experiment without knowledge of its true results it might result in some danger to the safety of those perforning it without knowledge of all the risks.
In salty water ions are produced by the salt
here salt is NaCl
so it will break in Na⁺ and Cl⁻
They carry the current
Na⁺ moves towards cathode and Cl⁻ moves towards anode
So current is carrying by ions which are Na⁺ and Cl⁻
Answer:
I'm not sure but I think it's 4.5 v
It will not explode since the mass of the cotton balls is so low but rather will most likely break the lock and hinges and come out.