60 lines
3.5 KiB
XML
60 lines
3.5 KiB
XML
<problem><startouttext/><br/><br/>You have a 6-volt battery (assumed ideal) and a 1.5-volt flashlight
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bulb, which is known to draw \(0.5 A\) when the bulb voltage is \(1.5 V\) (see
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figure below). Design a network of resistors to go between the battery
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and the bulb to give \(v_s = 1.5 V\) when the bulb is connected, yet
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ensures that \(v_s\) does not rise above \(2 V\) when the bulb is disconnected.
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<br/><br/><center><img src="/static/circuits/Lab1_1.png"/></center><br/><br/><i>Hint</i>: use a two-resistor voltage divider to create the voltage for node A. You'll
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have two unknowns (R1 and R2) which can be determined by solving the two equations for
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\(v_s\) derived from the constraints above: one involving R1, R2 and Rbulb where \(v_s = 1.5\), and
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one involving R1 and R2 where \(v_s = 2\).
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<br/><br/>There are two schematic diagrams below. Please enter the network
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of resistors you've designed into both diagrams. The top diagram is
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the model when the bulb is connected; the bottom diagram is the model
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when the bulb is disconnected.
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<br/><br/>Run a DC analysis on both diagrams to
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show that the node labeled "A" has a voltage of approximately
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\(1.5 V\) in the top diagram and less than \(2 V\) in the bottom
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adiagram. Submit your results <i>after</i> the DC analyses have
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been run (so the results of the analyses will be submitted too).
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<endouttext/>
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<schematicresponse><startouttext/>
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Schematic model when bulb is connected:
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<center><schematic height="270" width="400" parts="r" analyses="dc" initial_value="[["w",[48,88,48,112]],["L",[160,16,3],{"label":"A"},["A"]],["g",[48,112,0],{},["0"]],["w",[160,112,136,112]],["w",[160,88,160,112]],["w",[160,16,136,16]],["w",[160,40,160,16]],["r",[160,40,0],{"name":"Bulb","r":"3"},["A","1"]],["w",[48,112,72,112]],["w",[48,16,72,16]],["w",[48,40,48,16]],["v",[48,40,0],{"name":"Battery","value":"6V"},["2","0"]],["view",0,0,2]]"/></center>
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Schematic model when bulb is disconnected:
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<center><schematic height="270" width="400" parts="r" analyses="dc" initial_value="[["w",[48,88,48,112]],["L",[160,16,3],{"label":"A"},["A"]],["g",[48,112,0],{},["0"]],["w",[160,112,136,112]],["w",[160,88,160,112]],["w",[160,16,136,16]],["w",[160,40,160,16]],["w",[48,112,72,112]],["w",[48,16,72,16]],["w",[48,40,48,16]],["v",[48,40,0],{"name":"Battery","value":"6V"},["2","0"]],["view",0,0,2]]"/></center>
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<endouttext/>
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<answer type="loncapa/python">
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# for a schematic response, submission[i] is the json representation
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# of the diagram and analysis results for the i-th schematic tag
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correct = ['incorrect', 'incorrect'] # optimistic default :)
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def get_dc(json):
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for element in json:
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if element[0] == 'dc': return element[1]
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return None
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dc_with_bulb = get_dc(submission[0])
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if dc_with_bulb:
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v = dc_with_bulb['A']
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if v >= 1.4 and v <= 1.6: # want 1.5
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correct[0] = 'correct'
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dc_without_bulb = get_dc(submission[1])
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if dc_without_bulb:
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v = dc_without_bulb['A']
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if v <= 2.1: # want 2
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correct[1] = 'correct'
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</answer>
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</schematicresponse>
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</problem>
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