This document is the first half of chapter 8 from an engineering essentials course on internal resistance. It defines key terms like internal resistance, electromotive force (EMF), and terminal voltage. It explains that internal resistance decreases with larger plates and smaller distance between plates in a cell. The chapter objectives are to calculate EMF, terminal voltage, and current of a cell using the equation that the terminal voltage is equal to the EMF minus the internal resistance times the current. It provides examples of these calculations.

1. IT2001PA
Engineering Essentials (1/2)
Chapter 8 – Internal Resistance
Lecturer Name
lecturer_email@ite.edu.sg
Aug 16, 2012
Contact Number

2. Chapter 8 – Internal Resistance
Lesson Objectives
 Upon completion of this topic, you should be able to:
 Calculate the emf, terminal voltage and current of a cell..
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3. Chapter 8 – Internal Resistance
Specific Objectives
Students should be able to :
Explain the internal resistance of a cell.
Explain the electromotive force (EMF) of a cell.
Explain the internal resistance of a cell.
Statethat the emf of a cell can be calculate using the
equation E = V + Ir
IT2001PA Engineering Essentials (1/2)

4. Chapter 8 – Internal Resistance
Internal Resistance of a Cell
 Resistance offered by internal components of cell.
 Internal resistance, r, decreases () if
 Size of plate 
 Distance between plates 
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5. Chapter 8 – Internal Resistance
Internal Resistance of a Cell
where V = terminal voltage of cell
V = E – Ir E = open circuit voltage of cell
r = internal resistance of cell
V = IR R = load resistance
I = load current
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6. Chapter 8 – Internal Resistance
Electromotive Force (emf) of a Cell
 The emf (E) of a cell is the total voltage generated by the cell is
measured with the cell open-circuit (also called open circuit voltage of
cell).
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7. Chapter 8 – Internal Resistance
Terminal Voltage of a Cell
 The terminal voltage, or potential difference (p.d.) of a cell, is the
voltage across the cell terminals when the cell is supplying current to a
load.
 V is less than the value of E when the cell is supplying current to a load.
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8. Chapter 8 – Internal Resistance
Calculation on Cells
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9. Chapter 8 – Internal Resistance
Next Lesson
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