**Difference Between Ohmic and non-Ohmic Conductors:**

**Ohmic Conductors:**

**Ohm’s Law:**

I=V/R

Where,

V= Applied Voltage

I = Current in the circuit

R = Circuit Resistance

** **

**Non-Ohmic Conductors:**

The non ohmic conductor does not follow the Ohm’s Law, and the current drawn by the non ohmic conductor does not proportionately vary with the varying applied voltage.The resistance of non ohmic conductor does not remain constant when the voltage is applied across it. The changing resistance results in change in the current for a particular voltage and the V-I graph is no more linear.

If we take the slope of V-I curve of the above graphs the resistor has the constant slope because of constant slope. The filament has variable resistance because the slope of the V-I graph is not constant.

All the semiconductor devices are non-linear devices because the current drawn by the devices is not proportional to the applied voltage. The semiconductor devices have a barrier potential and when the applied voltage is increased above the barrier potential the device starts conducting. If the voltage is increased above the barrier potential the voltage across the device remains constant and the current starts increasing. This happens because the concentration of the holes and electrons increases as the current through the device is increased. ** The resistance of the PN junction is not constant and does vary with the flow of electric current through the junction. **The voltage and current has non linearity in the semiconductor junction diode.

Almost all the semiconductor devices which have nonlinear V-I relationship are as depicted below.

** **

**The V-I graph of the semiconductor diode has the exponential relationship.**

If we see the V-I curves of a semiconductor device, the current rises abruptly when the voltage reached the particular value. The diode current equation is as given below.

**Where,**

**Io= Saturation Current**

q= Charge of an electron- 1.6 *10^{–}^{19 }**Coulomb**

**K=Boltzmann Constant- 1.38 * **10^{– 23}^{ }**JK**^{–}^{1}

**T= Temperature(K)**

**The diode current increases exponentially when the voltage is increased above a particular value.**

The collector current does not vary proportionately with an increase in the collector to emitter voltage.

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