Level 1: Ammeter Connected Across a Battery by Mistake: What Happens?
Work out the actual current.
An ammeter of resistance 0.1 Ω is connected directly across a cell of EMF 2 V and internal resistance 0.4 Ω. The ammeter reads:
The ammeter and the cell's internal resistance are the only resistances in the loop, so they are in series and share the cell's EMF between them.
Ignoring the internal resistance gives 20 A, and ignoring the ammeter gives 5 A. A real cell always has some internal resistance, which is what keeps a short-circuit current finite.
Every Level 2 starts from a quick question, Level 1, and changes one thing. Seeing what that change does is the skill JEE Main tests. Try it here, free and with no signup, then read the worked answer.
