Exam 3 Ch. 25&26 ARC Spring 2018 hy ies 421 (100 pes) () Coneeptls ps each for 3
ID: 2036044 • Letter: E
Question
Exam 3 Ch. 25&26 ARC Spring 2018 hy ies 421 (100 pes) () Coneeptls ps each for 30 pas todal a) Explain the ditfenences and similarities between resistivity and resistance b) Define curent and explain which charge carriers are mobile in a conventional cendactor (metal c) How does the temperature affect the conductivity of a metal? A semiconductor? d) What causes a current to flow? What can slow it down? e) On the diagram below indicale how you would measure the current through and the voltage across the lightbulb Let indicate the multi-meter in DC voltage mode and indicate it in DC current mode. Clearly indicate the position of the leads in each scenario. 10) In a basic RC circuit indicate on the graph how the current would change in time as an initially fully charged capacitor is discharged over a resistance "R". Label the axis. Indicate how this curve would change if the resistance "R" were doubled without changing the capacitance value.Explanation / Answer
a)
Similarities :
Resistance and resistivity of a unit length and unit cross section of a material is same .
Resistance and resistivity of a material depends on the intrinsic property of the material.
Differences:
Resistivity of a material does not depend on its length or cross section whereas resistance does.
Unit of resistivity is ohm.meter whereas resistance has unit of ohm .
b)
Current is the rate of flow of charge carriers.
The mobile charge carriers in conductors are electrons.
c)
Most of the metals have higher conductivity as the temperature drops.
For semiconductors, the conductivity increases with increase in temperature.
d)
An Electric field causes the electrons to flow.
Resistance of the material impedes the flow of the electrons.
e)
To measure the voltage across the lightbulb, we place the two leads of the multimeter across the two ends of the lightbulb with the positive lead on the right of the bulb and the negative lead on the left.
To measure the current across the lightbulb, we place the negative lead of the multimeter on the positive terminal of the battery and the positive lead of the multimeter on the upper part of the circuit.
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