An ammeter should be connected in series in a circuit. This is because an ammeter is designed to measure the current flowing through the circuit, and current is the same at every point in a series connection. Also, an ammeter has very low resistance (nearly zero), so connecting it in series ensures the current flowing through the circuit also flows through the ammeter for accurate measurement. If an ammeter is connected in parallel, due to its low resistance, it would create a short circuit path, causing a large current to flow through the ammeter. This could damage the ammeter and produce erroneous readings. Hence, to avoid this and to get accurate current measurements, the ammeter must always be connected in series. In contrast, a voltmeter, which has very high resistance, is connected in parallel to measure voltage across components without altering the current significantly.
