Electric Circuits. Honors Physics

Transcription

1 Electric Circuits Honors hysics

2 Ways to Wire Circuits here are basic ways to wire a circuit. Keep in mind that a resistor could be ANYHNG ( bulb, toaster, ceramic material etc) Series One after another arallel between a set of junctions and parallel to each other

3 Schematic Symbols Before you begin to understand circuits you need to be able to draw what they look like using a set of standard symbols understood anywhere in the world For the battery symbol, the LONG line is considered to be the OSE terminal and the SHO line, NEGAE. he OLMEE and AMMEE are special devices you place N or AOUND the circuit to measure the OLAGE and CUEN.

4 he oltmeter and Ammeter Current goes HOUGH the ammeter he voltmeter and ammeter cannot be just placed anywhere in the circuit. hey must be used according to their DEFNON. Since a voltmeter measures voltage or OENAL DFFEENCE it must be placed ACOSS the device you want to measure. hat way you can measure the CHANGE on either side of the device. oltmeter is drawn ACOSS the resistor Since the ammeter measures the current or FLOW it must be placed in such a way as the charges go HOUGH the device.

5 Simple Circuit When you are drawing a circuit it may be a wise thing to start by drawing the battery first, then follow along the loop (closed) starting with positive and drawing what you see.

6 Series Circuit n in series circuit, the resistors are wired one after another. Since they are all part of the SAME LOO they each experience the SAME AMOUN of current. n figure, however, you see that they all exist BEWEEN the terminals of the battery, meaning they SHAE the potential (voltage). ( series) otal ( series) otal

7 Series Circuit ) ( ) ( otal series otal series As the current goes through the circuit, the charges must USE ENEGY to get through the resistor. So each individual resistor will get its own individual potential voltage). We call this OLAGE DO. i s series series otal series ) ( ) ( ; Note: hey may use the terms effective or equivalent to mean OAL!

8 Example A series circuit is shown to the left. a) What is the total resistance? (series) = + + = 6W b) What is the total current? = =(6) = A c) What is the current across EACH resistor? hey EACH get amps! d) What is the voltage drop across each resistor?( Apply Ohm's law to each resistor separately) W ()() W =()()= 6 W =()()= 4 Notice that the individual OLAGE DOS add up to the OAL!!

9 arallel Circuit n a parallel circuit, we have multiple loops. So the current splits up among the loops with the individual loop currents adding to the total current Junctions t is important to understand that parallel circuits will all have some position where the current splits and comes back together. We call these JUNCONS. he current going N to a junction will always equal the current going OU of a junction. ( parallel) otal egarding N OU Junctions :

10 arallel Circuit Notice that the JUNCONS both touch the OSE and NEGAE terminals of the battery. hat means you have the SAME potential difference down EACH individual his junction touches the OSE terminal his junction touches the NEGAE terminal branch of the parallel circuit. his means that the individual voltages drops are equal. ( parallel) otal ( parallel) otal ( ) arallel i ;

11 Example o the left is an example of a parallel circuit. a) What is the total resistance? p b) What is the total current?.0 W 8 ( ).64 A 8 8 5W 7W 5 7 c) What is the voltage across EACH resistor? 8 each! d) What is the current drop across each resistor? (Apply Ohm's law to each resistor separately).6 A.4 A 0.90 A 9W 8 9 Notice that the individual currents ADD to the total.

12 Compound (Complex) Circuits Many times you will have series and parallel in the SAME circuit. Solve this type of circuit from the inside out. WHA S HE OAL ESSANCE? s W ;.W

13 Compound (Complex) Circuits s W ;.W Suppose the potential difference (voltage) is equal to 0. What is the total current? 0 (.).06 A What is the OLAGE DO across the 80W resistor? 80W 80W 80W 80W 80W (.06)(80) 84.8

14 Compound (Complex) Circuits 80W 80W &.W 0.06A ( parallel) ( series) A What is the OLAGE DO across the 00W and 50W resistor? & & What is the current across the 00W and 50W resistor? 00W 5. Each! ( parallel) ( series) 50W & 0.5 A A Add to.06a