CHAPTER 13: Current Electricity & Circuits Adv. Physics 13.4 — Assignment Name: KEY (Answers) Hour: Date Ass’d: 4/22/15 Parallel Circuits 1. / 10 Series or Parallel? Identify each phrase as best describing a series (S) or parallel (P) circuit: (a) (b) (c) (d) (e) (f) (g) (h) (i) 2. ____ S ____ S ____ P ____ P ____ P ____ S ____ P ____ S ____ P ____ only one path for electrical current to flow current through a load is dependent on other loads how homes and businesses are wired current though a load is independent of other loads if one light turns off, the others stay on if you turn off one light, all the lights turn off has more than one path for the electrical current to flow the devices have the same current the voltage drop across each device is the same Two identical resistors in parallel. Two 10-ohm resistors are connected in parallel across a potential difference of 120 volts. (a) Draw the schematic diagram and calculate the equivalent (total) resistance of the circuit. 5Ω REQ = ______________ (b) Calculate the total current in the circuit. I TOT = 24 A 3. Three identical resistors in parallel. Now we add another resistor in parallel, so that three 10-ohm resistors are connected in parallel across the same 120-volt power source. (a) Draw the schematic diagram and determine the equivalent (total) resistance of the circuit. 3.33 Ω REQ = ____________ (b) Calculate the total current in the circuit. Compare to 2(b). I TOT = 36 A (1.5x more current after adding resistor in parallel) 1 of 2 CHAPTER 13: Current Electricity & Circuits Adv. Physics 4. 13.4 — Assignment Name: KEY (Answers) Hour: Date Ass’d: 4/22/15 Three unequal resistors in parallel. Loads of resistance 2 ohms, 1 ohm, and 6 ohms are connected in parallel across a 3 volt battery, as shown in the schematic diagram below. (a) What is the voltage drop across points A and H? H G F E 3V (b) What is the voltage drop across points B and G? ... C and F? ... D and E? 3V 3V 3V D + 2  B C Calculate the current flowing through the 2  resistor. I 2Ω = 1.5 A (d) Calculate the current flowing through the 1  resistor. I 1Ω = 3 A (e) Calculate the current flowing through the 6  resistor. I 6Ω = 0.5 A (f) Which resistor has the most current flowing through it? (g) Why? The 2 Ω resistor It has the LEAST RESISTANCE of all three resistors. (h) How does the amount of current flowing through the 2  compare with the 6  resistor? The 2 Ω has 3x more current than the 6 Ω. (i) Is the current in one branch proportional to or inversely proportional to the resistance of that branch? Explain briefly. The current is inversely proportional to branch resistance. (j) What is the equivalent (total) resistance of this circuit? R EQ = 0.60 Ω (k) 6 3V A (c) 1 What is the total current ( I TOT ) the battery provides to this circuit? I TOT = 5.0 A 2 of 2 D