Скачать или смотреть Class 8th l lesson no 4: Current Electricity And Magnetism

"Current electricity and magnetism" is a foundational topic in physics, usually studied under Electromagnetism. Here's a breakdown of the key concepts within this area:

⚡️ Current Electricity

1. Electric Current (I)

Definition: Flow of electric charge (usually electrons).

Unit: Ampere (A)

Formula:

I = \frac{Q}{t}

2. Potential Difference (V)

Definition: Work done to move a unit charge between two points.

Unit: Volt (V)

3. Ohm’s Law

 V = IR  where is voltage, is current, and is resistance.

4. Resistance (R)

Unit: Ohm (Ω)

Depends on:

R = \rho \frac{L}{A}

: resistivity of material

: length of the conductor

: cross-sectional area

5. Power in Electric Circuits

 P = VI = I^2R = \frac{V^2}{R} 

6. Electrical Energy

 E = Pt  where is energy, is power, and is time.

🧲 Magnetism

1. Magnetic Field (B)

Vector field produced by magnets, currents, or changing electric fields.

Unit: Tesla (T)

2. Magnetic Force

On a moving charge:

\vec{F} = q(\vec{v} \times \vec{B}) \vec{F} = I(\vec{L} \times \vec{B})

3. Biot–Savart Law
Describes magnetic field generated by a small segment of current-carrying conductor:

d\vec{B} = \frac{\mu_0}{4\pi} \frac{I d\vec{l} \times \hat{r}}{r^2}

4. Ampere’s Circuital Law

\oint \vec{B} \cdot d\vec{l} = \mu_0 I_{\text{enclosed}}

5. Electromagnetic Induction (Faraday’s Law)

Faraday's Law:

\mathcal{E} = -\frac{d\Phi_B}{dt}

Lenz’s Law: The direction of induced EMF opposes the change in flux.

6. Lorentz Force

Total force on a charged particle:

\vec{F} = q(\vec{E} + \vec{v} \times \vec{B})

🔄 Key Interconnections

Electric current produces magnetic fields (Oersted’s experiment).

Changing magnetic fields induce electric currents (Faraday's experiment).

These are unified under Maxwell’s Equations.

Would you like:

Concept maps or diagrams?

Example problems?

Practical applications?

Study guide for a specific exam?

Let me know how in-depth you'd like to go!