Ministry of Higher Education and Scientific Research AlMustansiriyah

Ministry of Higher Education and Scientific Research Al-Mustansiriyah University Faculty of Engineering Computer Engineering Department Electrical Eng. Lab 1' class Assistant Lecturer Hazim alkargole 2017 20189 ﻭﺯﺍﺭةﺎﻟﺘﻌﻠﻴﻢ ﺍﻟﻌﺎﻟﻲ ﻭﺍﻟﺒﺤﺚ ﺍﻟﻌﻠﻤﻲ ﺍﻟﺠﺎﻣﻌﺔ ﺍﻟﻤﺴﺘﻨﺼﺮﻳﺔ ﻛﻠﻴﺔ ﺍﻟﻬﻨﺪﺳﺔ ﻗﺴﻢ ﻫﻨﺪﺳﺔ ﺍﻟﺤﺎﺳﻮﺏ

CHAPTER 2 RESISTIVE CIRCUITS Ohm’s law : The voltage across a resistor is directly proportional to the current flowing through it. v (t) V (t) = R i(t) R≥ 0 The symbol of ohm is ( ) 1Ω 1 V 1 A R 1 i (t)

THE INSTANTANEOUS POWER P (T): P(t) v(t) i(t) R i(t) v(t) v 2 (t) R i (t) v(t) R R 2 2 v (t) P(t) v(t) i(t) R i 2 (t) R Note: Last equation says that the power at a resistor is always positive Resistors always absorb power. The inverse of resistance is conductance G 1 R

THE UNIT OF CONDUCTANCE IS SIEMENS (S) 1 S 1 A 1 V The current can be also expressed as i(t) GV(t) And the instantaneous power is i(t) i 2 (t) P(t) v(t)i(t) G G

P(t) v(t) i(t) v(t) G v(t) G v 2 (t) i 2 (t) v(t) i(t) G v 2 (t) G Open and short Circuits Open circuit ( R = ) circuit i(t) R= v(t) 0 R G=0 circuit Open circuit

Short circuit ( R = 0) circuit G= R= 0 v(t) Ri(t) 0 *i(t) 0 circuit Short circuit

I EXAMPLE : CONSIDER THE CIRCUIT: + - vs=12 v Find the current and power absorbed by the resistor I v s 12 v 6 m. A R 2 kΩ P v R I (12) (6 m) 72 m w R = 2 k

EXAMPL E: The power absorbed by a 10 k resistor in the circuit is 3. 6 m. W. I Find voltage and current in the resistor. I 2 3. 6*10 (10 *10 ) 3 I 3. 6 *10 7 0. 6 m. A V I R (0. 6 m A) (10 k ) V 6 V 3 - P R P I R vs + P Vs I I 2 R R 10 kΩ