Simple Resistive Circuites Lecture 3

Resistors in Series Series-connected circuit elements carry the same current The seven resistors can be replaced by a single resistor

Examples (Series):

Resistors in Parallel Parallel -connected circuit elements have the same voltage across their terminals

Resistors in Parallel Two resistors

Examples (Parallel):

Equivalent Resistance

Equivalent Resistance 30 Ω 5 kΩ 80 Ω

(p3.5, p3.6, p3.7, and assessment problem 3.1) Use Ohm’s law, KCL & KVL H.W. #4 (p3.5, p3.6, p3.7, and assessment problem 3.1) 15kΩ     75W 192W 500W

Voltage-divider circuits

Assessment Problem 3.2

Current-divider circuits  

Assessment Problem 3.3

H.W. #5 (Assessment problem 3.4, p3.15(a, b))

Measuring Voltage and Current Digital meters and Analog meters An Ammeter: instrument to measure current. Placed in series with the circuit element whose current is being measured. A Voltmeter: instrument to measure voltage. Placed in parallel with the circuit element whose voltage is being measured. Two categories of meters used to measure voltage and current: Digital meters and Analog meters

Measuring Resistance: The Wheatstone Bridge is a circuit used to precisely measure resistance of medium values in the range of 1Ω to 1M Ω. Consists of four resistors, a dc voltage source, and a detector (galvanometer). One of the four resistors can be varied (R3). To find the value of Rx, we adjust the variable resistor R3 until there is no current in the galvanometer. We then calculate the unknown resistor from the simple expression:  

Delta-to-Wye (∆-to-Y)(Pi-to-Tee) equivalent circuits The interconnected resistors can’t be reduced by the simple series or parallel equivalent circuits A ∆ configuration viewed as π configuration A Y structure viewed as T structure ∆-to-Y equivalent circuit Y -to- ∆ equivalent circuit

Assessment Problem 3.8

H.W. #6 3.55, 3.56(a & b)