Why do voltmeters have high input impedance?

A voltmeter is connected in parallel across the components of a circuit you want to measure. Whenever you connect an instrument in parallel, it naturally creates an alternate path for the current to flow. If the voltmeter had a low input impedance, it would draw a significant amount of current away from the component being tested. This phenomenon, known as the 'loading effect,' alters the circuit's normal operation and artificially drops the voltage you are trying to measure. By designing voltmeters with very high input impedance (often in the tens of megaohms), they draw virtually zero current. This ensures the circuit behaves exactly as it would if the meter were not connected, allowing for an accurate voltage reading.