Circuit Questions.docx



Circuit Analyzing Questions - Practice ProblemsV = IRqe = -1.6 * 10-19P=WtOhm’s WheelVariableConceptUnitNotesQChargeCoulombs (C)If number of electrons is given, you can find charge. If you are looking for number of electrons, use charge.ICurrentAmps (A) ; 1A = 1C/1sRate at which the charge flows through a circuit. (Also a measure of Coulombs/second)VVoltage (Electric Potential Difference)Volts (V) ; 1V = 1J/1CA circuit cannot exist without an electric potential difference. (Also a measure of Work/charge)RResistanceOhms (?)Resistance acts as an obstacle for the current. Resistance is the slope of a Current vs. Voltage Graph.PPowerWatts (W) ; 1W = 1J/1sPower is a measure of the amount of energy/second that each element of the circuit uses. WWorkJoules (J)Work is a form of energy.OHMS LAWYou connect a 75 ? resistor to a 9 V battery. What is the current through the resistor?You put a light bulb in a circuit with a 9 V battery. The ammeter shows that the current though it is 0.07A. What is the resistance of the bulb?A person accidentally touches a 120 V electric line with one hand while touching a ground wire with the other hand. Determine the current through the body when the hands are dry (100,000 ? resistance) and when wet (5000 ? resistance).If a long wire is connected to the terminals of a 12 V battery, 3.6 x 1019 electrons pass a cross section of the wire each second. Determine its resistance.As the potential difference in volts across a thin platinum wire increases, the current in amperes changes as follows: (I, V) = (0, 0), (0.112, 1.0), (0.337, 3.0) and (0.675, 6.1). Plot a graph of current vs. potential difference and indicate whether the platinum wire satisfies Ohm's law. If so, what is the resistance of the wire?Use the Ohm's law equation to provide numerical answers to the following questions:a. An electrical device with a resistance of 3.0 Ω will allow a current of 4.0 amps to flow through it if a voltage drop of ________ Volts is impressed across the device.b. When a voltage of 120 V is impressed across an electric heater, a current of 10.0 amps will flow through the heater if the resistance is ________ Ω.c. A flashlight that is powered by 3 Volts and uses a bulb with a resistance of 60 Ω will have a current of ________ Amps.POWERA 1500-W hair dryer is plugged into the outlet (household voltage from outlets are 120 V) in your bathroom. How much current does this hair dryer draw?How many 60-W incandescent light bulbs can be operated at the same time on a 120-V, 15-A circuit in a home? How many energy-efficient 22-W fluorescent bulbs can operate on a similar circuit?A color TV has a current of 1.99 Amps when connected to a 120-Volt household circuit. What is the resistance (in ohms) of the TV set? And what is the power (in Watts) of the TV set?SERIES CIRCUITSRemember that in a series circuit:the current in every part of the circuit (is the same, adds up).the voltage supplied by the battery is the _________ voltage of the circuit, and thevoltage drops across each resistor (is the same, adds up to) the total voltage.to calculate total resistance, (add, use reciprocals). Solve the following for their equivalent resistance (total resistance).a. Three 5-Ω resistors placed in series would provide a resistance that is equivalent to one _____-Ω resistor.b. Three resistors with resistance values of 2-Ω , 4-Ω , and 6-Ω are placed in series. These would provide a resistance that is equivalent to one _____-Ω resistor.c. Three resistors with resistance values of 5-Ω , 6-Ω , and 7-Ω are placed in series. These would provide a resistance that is equivalent to one _____-Ω resistor.d. Three resistors with resistance values of 12-Ω, 3-Ω, and 21-Ω are placed in series. These would provide a resistance that is equivalent to one _____-Ω resistor.The following chart represents a set of three resistors arranged in series. Draw a diagram of the circuit to the right of the table. Then use what you know about series circuits to fill in the empty spaces.VIRTotal120 VR110 ΩR25 ΩR325 ΩThree resistors of 8 Ω, 6 Ω, 4 Ω, are connected in series to a battery of six 1.5-V dry cells, which are also connected in series.Draw the circuit diagram for this situationCalculate the total voltage provided by the battery.Calculate the total resistance.Find the total current.What is the voltage drop across each individual resistor?PARALLEL CIRCUITSRemember that in a parallel circuit:the current in the branches of the circuit (is the same, adds up).the voltage drops across each branch (is the same, adds up to) the total voltage. to calculate total resistance, (add, use reciprocals).Solve the following for their equivalent resistance (total resistance).Req = _________Req = _________Req = _________Req = _________Req = _________Req = _________Which circuit segment below has the same total resistance as the circuit segment shown in the diagram to the left?240030038100266700133350A 6 Ω, 3 Ω, and 18 Ω resistor are connected in parallel to an 18-V power supply. Find:the total resistance of the circuitthe total current through the circuitthe current flowing through each resistorThe following chart represents a set of three resistors arranged in parallel. Draw a diagram of the circuit to the right of the table. Then what you know about parallel circuits to fill in the empty spaces.VIRTotal24 VR118 ΩR212 ΩR336 ΩUse the given information from the diagram to solve for any missing current, voltage, or resistance values.Answers:Ohm’s Law0.12 A 128.6 Ω0.0012 A, 0.024 A2.1 ΩYes, 9 Ω12 V, 12 Ω, 0.05 APower12.5 A30 lights, 81 lights60.3 Ω, 238.8 WSeries Circuitis the same, total, adds up to, add15 Ω, 12 Ω, 18 Ω, 36 Ω30 V, 15 V, 75 V, 3 A, 3 A, 3 A, 3 A, 40 Ω9 V, 18 Ω, 0.5 A, 4V, 3V, 2VParallel Circuitadd up, is the same, use reciprocals1 Ω, 2 Ω, 8/3 Ω, 2 Ω, 8/17 Ω, 16/33 ΩD1.8 Ω, 10 A, 3 A, 6 A, 1 A24 V, 24 V, 24 V, 4 A, 1 ? A, 2 A, ? A, 6 Ω30 V, 30 V, 3 A, 2 A, 6 Ω, 5 A8 Ω, 3 A, 24 V, 24 V, 2 A, 1 A ................
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