The graph shows V-I curves for two conductors. One is measured for a carbon resi

Question

The graph shows V-I curves for two conductors. One is measured for a carbon resistor and obeys Ohm's law; the other is for a light-emitting diode (LED) and shows non-ohmic behaviour. What is the resistance of the carbon resistor?=10ohm

RESISTANCE FOR CARBON RESISTOR IS 10 ohm

For what value of current is the resistance of the LED the same as that of the carbon resistor? (Use a ruler and a triangle to draw on the diagram.)

Explanation / Answer

The curve is bewteen V and I.

So, the value of resistance R is just the slope of the curve.

In the first case we find that the slope the curve for carbon resistor = 2.0 / (200 x 10^-3) = 10

So, resistance of the carbon resistor = 10 ohm

Second Part -

Now for the same value of resistance of LED , find the point on the non-ohmic curve where the tangent = 10 ohm.

Just using my eyeball, I'd say it's around the 140mA range.
Please bote that it is just a visual solution through the graph.

It has NOTHING to do with where the curves themselves intersect -- just where they are parallel.

So, the answer of the second part of the question = 140 mA.

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