1. Conventional Current

2. When we speak of the current flowing in a circuit, we mean the direction positive charge would flow.

3. Important: Current is not a vector, it’s a scalar!!!!

4. Important : In any single circuit, the current at any instant is the same at one point as at any other point!!! This follows from the conservation of electric charge.

5. Ohm’s Law: Resistance and Resistors
I~V

6. Definition of Resistance
I=V/R

7. Ohm’s Law
The current through a metal conductor is proportional to the applied voltage.

8. Resistivity

10. Conceptual Example: Stretching Changes Resistance
A wire of resistance R is stretched uniformly until it is twice its original length. What happens to its resistance?

11. Effect of Temperature

12. a – temperature coefficient of resistivity is positive for metals and negative for semiconductors.

13. Superconductivity