Let us take a positively charged ball and a negatively charged ball and join them with a metal rod. Now if we connect one end of a wire with the positively charged one and the other end of the wire with a negatively charged one,shouldn't there be a flow of electricity(i.e a bulb lights up)? Because the balls+rod system is behaving like a battery here since positive charge is at one end and negative charge is at the other hand meaning higher potential(positive charge) and lower potential(negative charge) at two ends. So here is potential difference. Also since the balls are joined with a metal rod,electrons can pass through the rod after coming at the positively charged ball and hence constant flow of electrons can be ensured. I know this isn't possible in real life. So where am I making the flaws?
Also since the balls are joined with a metal rod,electrons can pass through the rod after coming at the positively charged ball and hence constant flow of electrons can be ensured
Your analysis is correct up until this point. The flow will not be constant. There will be a very high initial current and (assuming the wire doesn’t melt) then the current flow will stop.
The issue is that there is nothing replenishing the charge. You have no return path for the current to make a closed circuit. So the current will simply reduce the charge on both balls, and once they are drained the current will stop flowing.
The bulb needs constant flow of electrons to glow, but here there is no constant flow because once to attach the metal rod to the charged balls the negative charge starts to move towards the positive charge just because u gave the path of electrons to travel(i.e.,metal rod).Thus joining charge difference u created a potential difference which last until the the charge on the balls reach their equilibrium. By using a battery systems u create continuous flow of electrons through chemical reactions inside the battery.By the way, I want tell u just keep going this a nice way to learn concepts.When there is will there is a way!!