resistance (ten-ohm resistor) = 10.0645 volt/amp resistance (100 ) = 99.635 volt
ID: 1429103 • Letter: R
Question
resistance (ten-ohm resistor) = 10.0645 volt/amp
resistance (100 ) = 99.635 volt/amp
Questions
1. Compare the ratio of voltage and current from the Scope display to the resistance of the resistor(s) used.
2. Does each resistor you used have a constant resistance?
3. Does the light bulb filament have a constant resistance (constant ratio of voltage to current? Why or why not?
4. The slope of the graph for the light bulb is not symmetric. Why is the trace on the Scope different when the filament is heating up compared to the trace when the filament is cooling down?
Explanation / Answer
1).
Use Ohm's Law, V = I*R.
Let's say we have a V source with a resistance of 10 ohms. The current will = V/10 A.
Let's say we have a V source with a resistance of 100 ohm . The current will = V/100 A.
Therefore, the current decreases as R goes up (given constant voltage) and increases as R goes down.
3).
An ohmic resistor is one in which the value of the resistor does not change over a fairly wide range of applied voltages and currents.
That being said, a light buld is definitely NOT an ohmic resistor. Its resistance value changes considerably over the voltage range between zero and it's rated voltage.
4).
Starting from cool you apply a current..at the beginning of the trace there is relatively little resistance and the filament glows dull red,milliseconds later the temperature of the filament increases and raises the Resistance until it reaches the maximum brightness of white...In other words the inrush of current is in inverse proportion to the resistance (limited by heat)..now when the current is removed there is no parabolic ramp to tangency there is only a linear drop to zero,even while the filament is still white hot (a residual effect) no current is flowing..Another point to make here is the relationship you noticed here holds true for practically all loads .when the power is removed there is no residual current to contend with only a ramp down from heat which of course is as linear as the ambient temperature will allow... Well there ya go from the E
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