Why should an ammeter have low resistance?

Hey there! Great question about ammeters. The reason ammeters need low resistance is actually pretty fundamental to how they work. An ammeter is designed to measure the current flowing through a circuit, and to get an accurate reading, it shouldn't alter the current itself.

If an ammeter had high resistance, it would significantly reduce the current in the branch where it's connected, giving you a false reading of what the current would have been without the meter. By having very low resistance, the ammeter minimizes its impact on the circuit, allowing it to measure the true current flowing. Think of it as trying to listen to a conversation without interrupting - the ammeter just "listens" to the current without changing it!

As an electrical engineer, I can give you the technical explanation. Ammeters are connected in series with the circuit components. According to Ohm's Law (V = IR), for a given voltage, current is inversely proportional to resistance. When you add an ammeter in series, you're adding its resistance to the total circuit resistance.

If the ammeter resistance is significant, the total resistance increases, causing the current to decrease. This would defeat the entire purpose of measurement! Quality ammeters typically have resistances of less than 0.1 ohms to ensure they don't appreciably affect the circuit being measured. This is why you should never connect an ammeter in parallel with a component - the low resistance would create a short circuit!