Recap of Chapter 25-28

Electric Currents and Resistance

Units
Current	1 A = 1 C/s
Potential difference	1V = 1 J/C
Power	1 W = 1J/s
Resistance	1 $\Omega$ = 1 V/A

• An electric battery serves as a source of nearly constant potential difference.
• Electric current, $I$, refers to the rate of flow of electric charge and is measured in amperes (A): 1 A equals a flow of 1 C/s past a given point.
• The direction of conventional current is that of positive charge flow. In a wire, it is actually negatively charged electrons that move, so they flow in a direction opposite to the conventional current.
• Positive conventional current always flows from a high potential to a low potential.
• The resistance $R$ of a device is defined through the Ohm’s law

$V=IR$

• The current $I$ coming from a battery of voltage $V$ depends on the resistance $R$ of the circuit connected to it.