In an open circuit, a voltmeter in parallel to a battery measures the EMF. Once the circuit is closed, the measured voltage drops due to both the internal and the external resistance. My question is how can the initial resistor not affect the voltage the voltmeter measures? Additionally, Because an ideal voltmeter has infinite resistance, how can a voltmeter measure voltage without the electrons from the current? It's like, how can I measure the potential energy of a ball without the ball? Also, if voltage is like potential energy, then why does potential difference equal to zero after it passes the last resistor, and not when it reaches the end of the wire? I'm sorry that these questions are basic. I just hope to gain a decent understanding of the material. Thank you to anybody who is so kind as to help me out.