online assignment 4-2-1

online assignment 4-2-1 - MasteringPhysics: Assignment...

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Manage this Assignment: 3a. Electric Currents Due: 11:00pm on Sunday, January 24, 2010 Note: To understand how points are awarded, read your instructor's Grading Policy . Print Version with Answers Alternating Voltages and Currents Description: Find the rms voltage from the graph of the instantaneous voltage; then find the rms current and average power from a given value of R. The voltage supplied by a wall socket varies with time, reversing its polarity with a constant frequency, as shown in the graph. Part A What is the rms value of the voltage plotted in the graph? Express your answer in volts. Hint A.1 RMS value of a quantity with sinusoidal time dependence A quantity that varies with time as (or ) has a maximum value equal to and an rms value given by . Hint A.2 Find the maximum value of the voltage What is the maximum value of the voltage plotted in the graph? Express your answer in volts. ANSWER: = Page 1 of 10 MasteringPhysics: Assignment Print View 1/8/2010 http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1327097
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This is the standard rms voltage supplied to a typical household in North America. ANSWER: = Part B When a lamp is connected to a wall plug, the resulting circuit can be represented by a simplified AC circuit, as shown in the figure. Here the lamp has been replaced by a resistor with an equivalent resistance = 120 . What is the rms value of the current flowing through the circuit? Express your answer in amperes. Hint B.1 Ohm's law in AC circuits Ohm's law can still be applied to an AC circuit, provided the values used to describe all physical quantities are consistent. For example, Ohm's law can be written using maximum values of voltage and current, or alternatively using rms quantities. ANSWER: = Part C What is the average power dissipated in the resistor? Hint C.1 Average power in an AC circuit The average power dissipated in a resistor with resistance is given by , where is the rms value of the current flowing through the resistor. Note that the average power can also be Page 2 of 10 MasteringPhysics: Assignment Print View 1/8/2010 http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1327097
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Express your answer in watts. The instantaneous power dissipated in the resistor can be substantially higher than the average power. However, since the voltage supplied to the resistor varies in time, so does the instantaneous power. Therefore, a better estimate of the energy dissipated in an AC circuit is given by the average power. For example, the power rating on light bulbs is in fact the average power dissipated in the bulb. expressed as , where is the rms voltage supplied to the resistor . ANSWER: = Electrical Resistance and Temperature Conceptual Question Description: Conceptual question on the temperature dependence of electrical resistance. Requires the student to interpret a graph of resistance versus temperature. The electrical resistance of most materials is dependent on temperature. For many materials, the resistance decreases
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This note was uploaded on 07/01/2010 for the course PHYS 101213 taught by Professor Bratton during the Spring '10 term at CSU Chico.

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online assignment 4-2-1 - MasteringPhysics: Assignment...

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