1. Electric Current
Physics 2

2. Topic Outline
• Electric Current
• Ohm’s Law
• Resistivity
• Electric Power
• Resistors in Series
• Resistors in Parallel
• Series‐Parallel Resitors

3. Electric Current

4. Two Conditions in order for Electric
Current to Exist
1. There must be a conducting path between
the two points along which charge can flow.
1. There must be a difference of potential
between the two points. A large potential
difference means a large “push” given to
each charge.

5. Electric Current Analogous with Flow
of Water

6. Resistance

7. Example:

8. Ohm’s Law
Ohm’s Law was experimentally verified by
Georg Ohm (1787 – 1854) which states that
the current is proportional to voltage in many
substances.
Ohm’s Law is not the same definition of
resistance, R=V/I. Ohm’s Law holds only for
conductors in which R is constant.

9. Resistivity

10. Resistivity of Material

11. Example:

12. Temperature Variation of Resistivity

13. Example:

14. Electric Power

15. Example:
A solar cell 10 cm in diameter produces a current of 2.15 A at 0.45‐
V in bright sunlight whose intensity is 0.10 W/cm2. Find the
efficiency of the cell.

16. Resistors in Series
Resistors in series are joined end‐to‐end, so the
same current is present in all of them.

17. Example:

18. Resistors in Parallel
Resistors in parallel have their ends connected
together so that the total current is split up among
them.

19. Example:

20. Series‐Parallel Combination

21. REFERENCE:
Modern Technical Physics 6th Edition by
Arthur Beiser
Copyright © 1992 by Addison‐Wesley
Publishing Company, Inc.