Resistivity and Voltage in Intrinsic and Extrinsic Silicon Samples

[lazyaditya]

Homework Statement

The resistivity at room temperature of intrinsic silicon is 2.3*10³ Ωm and that of an "n" type extrinsic silicon sample is 8.33*10^-2Ωm . A bar of this extrinsic silicon with 50*1000 mm has a steady current of 100μA across it. The voltage across the bar is found to be 50 mVolt.If the same bar is of intrinsic silicon,the voltage across the bar will be ?

Homework Equations

The Attempt at a Solution

 

[mfb]

I think you forgot to fill out part 2 and 3 of the homework template. In other words: What do you know about conduction? What did you do so far? Where did you run into problems?

 

[lazyaditya]

I think you forgot to fill out part 2 and 3 of the homework template. In other words: What do you know about conduction? What did you do so far? Where did you run into problems?

The thing is i solved the question by using ohm's law but when i asked someone they said current flow through semiconductor is not linear and it won't follow V=IR so that is why i was confused.

 

[marcusl]

There is a point where deviations from Ohm's law appear due to collision processes caused by very high internal electric fields. This is called the "hot electron" regime. It takes some effort to get there, however, so you needn't worry about it for common and practical systems. Ohm's law works fine in general.

 

[rezeew]

I would like to first clarify the concepts of resistivity and voltage. Resistivity is a measure of a material's ability to resist the flow of electric current, while voltage is the potential difference between two points in an electrical circuit.

Given the information provided, we can calculate the resistance of the extrinsic silicon sample using Ohm's Law, which states that resistance (R) is equal to the voltage (V) divided by the current (I). Using the given values, we can calculate the resistance of the extrinsic silicon sample to be 500 Ω (R = V/I = 50 mV/100 μA = 500 Ω).

To find the voltage across the bar if it were made of intrinsic silicon, we can use the formula for resistance (R = ρ*L/A) where ρ is the resistivity, L is the length of the bar, and A is the cross-sectional area. We can rearrange this equation to solve for voltage (V = I*R = ρ*L*I/A). Since the length and cross-sectional area of the bar remain the same, the only variable that changes is the resistivity. Therefore, if the bar were made of intrinsic silicon, the voltage across it would be 0.116 mV (V = 100 μA * 2.3*103 Ωm / (50*1000 mm * 1 mm^2) = 0.116 mV).

In conclusion, the voltage across the bar would be significantly lower if it were made of intrinsic silicon due to its higher resistivity compared to the extrinsic silicon sample. This highlights the importance of understanding the differences between intrinsic and extrinsic materials in electrical circuits.