CELL EMF:

The size of a cell has no bearing on the emf that it will produce, the generated emf being determined solely by the materials used in its construction. Another point to note is that the potential difference, or voltage measured across the terminals of a cell, is not the same as the emf generated by the cell. The terminal voltage of a cell depends on the:

• internal resistance of the cell.
• size of the discharge current.
• charge state of the cell.
• The size of the discharge current. As a general rule, whenever a cell is providing current, the terminal voltage will be less than the cell emf. The larger the discharge current, the greater the difference between the cell emf and its terminal voltage.
• The internal voltage of the cell. All sources of electricity have internal resistance which affects the terminal voltage, this will be examined in more detail later in the notes.