1 Basic Concepts Discussion D1.2 Chapter 1

2 Basic Concepts System of Units Charge Current and Voltage Power and Energy Ideal Circuit Elements

3 International System of Units (SI) Quantity Basic Unit Symbol Length meter m Mass kilogram kg Time second s Electric current ampere A Thermodynamic temperature kelvin K Luminous intensity candels cd

4 SI Prefixes MultiplierPefixSymbol terraT 10 9 gigaG 10 6 megaM 10 3 kiloK decid milim micro  nanon picop

5 Examples Express 1 ms/1000 in SI units. Not too long ago, computer disk space was measured in Mbytes. Modern disks have about 10,000 times more storage capacity. In SI units, what is the capacity unit of modern disks?

6 Charge, q Recall Coulomb’s Law Unit: Newton meter 2 / coulomb 2 volt meter / coulomb Charge on an electron (proton) is negative (positive) and equal to x C Force F 1 on charge q 2 due to charge q 1 is given by Note: Positive force is repulsive, negative force is attractive

7 Electric Current, i Current (in amperes) (A) is the time rate of change of charge q 1 A = 1 C/s Charge flowing past a point in the interval [t 0, t] is Convention: Direction of current flow is that of positive charges, opposite to the direction of electron flow

8 Voltage The energy in joules (w) required to move a charge (q) of one coulomb through an element is 1 volt (V). 1 volt = 1 joule/coulomb = 1 newton meter/coulomb

9 Power and Energy Power (p), in watts (W), is the time rate of expending or absorbing energy (w) in joules

10 Power and Energy Change in energy from time t 1 to time t 2 Passive sign convention: + - If p > 0 power is absorbed by the element If p < 0 power is supplied by the element

11 Circuit Elements Independent Voltage Sources

12 Circuit Elements Independent Current Source

13 Circuit Elements Dependent Voltage Sources

14 Circuit Elements Dependent Current Sources

15 Passive Circuit Elements i i i + -