hydrogen one lies further to the left. That means that there will be less build-up of electrons on the copper than there is on the platinum of the hydrogen electrode. There is less difference between the electrical charges on the two electrodes, so the voltage measured will be less. This time it is only 0.34 volts. The other major change is that this time the copper is the more positive (less negative) electrode. The voltmeter will show the hydrogen electrode as the negative one and the copper electrode as positive. The voltmeter You may have noticed that the voltmeter was described further up the page as having a "high resistance". Ideally, it wants to have an infinitely high resistance. This is to avoid any flow of current through the circuit. If there was a low resistance in the circuit, electrons would flow from where there are a lot of them (around the magnesium, for example) to where there are less (on the hydrogen electrode). If any current flows, the voltage measured drops. In order to make proper comparisons, it is important to measure the maximum possible voltage in any situation. This is called the electromotive force or emf . The emf of a cell measured under standard conditions is given the symbol E cell . Note: You read E as "E nought" or "E standard". For technical reasons to do with the way that people use different browsers which may be set to display text differently, it has been difficult