If one bulb broke in series circuit the other will light up ?

It makes no difference whether there are two bulbs or 1000 bulbs. If they are all in series then when one bulb burns out, or one little piece of wire between two bulbs comes loose, ALL of them go dark. In that situation it's a challenge to find where the break in the circuit is because all of the bulbs are dark.

100 pounds is 100 pounds no matter the object or item being weighed