First time I used my continuity tester, the bulb went bad. What happened?

Most likely they were testing a live circuit. Continuity testers are designed to test UNENERGIZED circuits. The bulbs in these testers are only rated for around 3 volts. If you hook this up to a live circuit in your house, you just put 120 volts through the bulb and that is why it blew out.

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