Why is it a very bad idea to connect an ammeter directly across a voltage source?
Connecting an ammeter directly across a voltage source can cause a short circuit, damaging the ammeter and potentially causing overheating or even a fire hazard. This is because an ammeter has a low resistance, which could cause a very high current to flow through the circuit, overwhelming the device and damaging it. It is important to always connect an ammeter in series with the circuit to measure current accurately and safely.