physics-class-12-unit-03-chapter-01-electric-current-and-current-density-l-1-11-j8xvjeed8ae

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Electric Current </primary>
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- Flow of charges.
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- $Q=Q_{+}-Q_{-} $

- $\quad \quad \propto$ time $t$

- Rate of flow

- $\quad \quad  I=\frac{Q}{t}$

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<footer style = "font-size: 18px">Electric Current and Current Density $\rightarrow$ Aurora Borealis (Northern Light) $\rightarrow$ <span style = "color:blue"> Electric Current </span> $\rightarrow$ Electric Current $\rightarrow$ Lightening </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Electric Current </primary>
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- $\Delta t$

- $\Delta Q$

- $I(t)=\text{Lim}_{\Delta t \rightarrow 0} \frac{\Delta Q}{\Delta t}=\frac{d Q}{d t}$

- $\text { Units } \frac{\text { Coulomb }}{\text { Second }}=\text { Ampere }$

- **S.I.** A Fundamental SI unit.

- 220-240V Household appliances. $\sim 5 \text { A }$

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<footer style = "font-size: 18px">Aurora Borealis (Northern Light) $\rightarrow$ Electric Current $\rightarrow$ <span style = "color:blue"> Electric Current </span> $\rightarrow$ Lightening $\rightarrow$ How is Current Created ? </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Conductors </primary>
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* Pressure, Temperature

* Conductors,(Silver, Copper, Aluminium Hg)

* Readily conduct electricity

* Eletron gas, Free electrons

* Belong to whole material

- **electrostatics** : Conductors

- $\vec{E}_{inside}=0$ : Not true under dynamic conditions

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<footer style = "font-size: 18px">Lightening $\rightarrow$ How is Current Created ? $\rightarrow$ <span style = "color:blue"> Conductors </span> $\rightarrow$ Electrolytes $\rightarrow$ Insulators and Semiconductors </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Insulators and Semiconductors </primary>
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- **Insulators**

- Tightly bound electrons.

- $E_{inside}$ need not be zero

- **Semiconductors**

- Metals Electrostatics

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<footer style = "font-size: 18px">Conductors $\rightarrow$ Electrolytes $\rightarrow$ <span style = "color:blue"> Insulators and Semiconductors </span> $\rightarrow$ Dynamic Condition $\rightarrow$ Direction of Current </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Dynamic Condition </primary>
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- **Charge pump**
	
- No internal electric field will be created.

- $E_{int}$ = 0
	
- Hence charge flow current.

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<footer style = "font-size: 18px">Electrolytes $\rightarrow$ Insulators and Semiconductors $\rightarrow$ <span style = "color:blue"> Dynamic Condition </span> $\rightarrow$ Direction of Current $\rightarrow$ Current Density </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
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- Direction of flow of positive charge

- $I$ has a direction but is a scalar

- $\frac{dQ} {dt}$ = I

- Q = through a surface

- = $\int {Idt}$

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<footer style = "font-size: 18px">Insulators and Semiconductors $\rightarrow$ Dynamic Condition $\rightarrow$ <span style = "color:blue"> Direction of Current </span> $\rightarrow$ Current Density $\rightarrow$ Electrostatic Condition </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Current Density </primary>
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- **Current Density is a vector**

- |J| = $\frac{I}{Area}$

- Since $\vec{J}$ is a vector, we need to give a direction

- $\overrightarrow{d S}$ : a direction perpendicular to the cross section

- $\vec{J}$ : In the direction of current flow

- $\vec{J}.\vec{dS}$ > 0

- For positive current

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<footer style = "font-size: 18px">Dynamic Condition $\rightarrow$ Direction of Current $\rightarrow$ <span style = "color:blue"> Current Density </span> $\rightarrow$ Electrostatic Condition $\rightarrow$ Dynamic Conditions </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Electrostatic Condition </primary>
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- No electric field.
	
- Thermal  velocity $\sim$ ${10^6}$ m/s

- $\vec{E}_{inside}=0$

- Elastic collision

- Velocities of different electrons are uncorrelated.

- $\frac{1}{N} \sum_{i=1}^N\left\langle\vec{v}_i\right\rangle=0 $

- Average velocity of the collection of electrons is Zero.
	
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<footer style = "font-size: 18px">Direction of Current $\rightarrow$ Current Density $\rightarrow$ <span style = "color:blue"> Electrostatic Condition </span> $\rightarrow$ Dynamic Conditions $\rightarrow$ Drift Velocity </footer>

### <Success style="font-size:25px"> Electric Current And Current Density L-1 </Success>
### <primary style="font-size:24px"> Drift Velocity </primary>
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- All electrons within a volume AL will pass through that right face

- n = electron density
 
- Q = (en)LA
 
- e = Magnitude of electron charge = 1.6 x $10^{19}$ c

|J|= $ \frac{Q}{A t} = e n \frac{L}{t} =  en v_\alpha $
 
 - ${\vec{J}=-e n \vec v_\alpha} $

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<footer style = "font-size: 18px">Electrostatic Condition $\rightarrow$ Dynamic Conditions $\rightarrow$ <span style = "color:blue"> Drift Velocity </span> $\rightarrow$ Thank You $\rightarrow$  </footer>