2026-05-19 06:46

Status: #new

Tags: #physics #electromagnetism

Electromagnetic Induction

Brief Overview

• Magnetic fields cause electric current (when motion occurs such that the fields are changing)
• Changing magnetic fields cause a coils electric fields to be changing such that charges are moved
• Induces current and Voltage $\to$ faster motion, stronger current

Alternating Current

• Electromagnetic induction acting in a direction rel. to the magnet is the reason WHY we can change the direction of current...

Faradays Law

• ${ϵ}_{induced}=-\frac{\mathrm{\Delta }\varphi }{\mathrm{\Delta }t}$ , $\varphi$ rep. magnetic flux
• $\Vert {ϵ}_{induced}\Vert =\Vert \frac{\mathrm{\Delta }\varphi }{\mathrm{\Delta }t}\Vert \cdot n$, n rep. number of loops
• At a instant of time: $\Vert {ϵ}_{induced}\Vert =\Vert \frac{\mathrm{\Delta }d\varphi }{\mathrm{\Delta }dt}\Vert \cdot n$

Lenz's Law

• The opposite of the change in flux is the induce current
  • $\to$ Induced current goes AGAINT change in flux..
    

Lenz's Law and Motors....

The Ideal Transformer

• We know a changing electric current $\to$ changing magnetic field
• Thus we can use this to induce a voltage and current in a secondary coil
• Voltage can be stepped up or stepped down as needed
• In a ideal transformer, we assume that it is 100% efficient (no energy loss)
• $\to$ Primary power = Secondary power...
• Illustration:
  

Some Formulas...

• $\frac{V_P}{V_S}=\frac{I_S}{I_P}=\frac{N_P}{N_S}$ , explained by $V_P{I}_P=V_S{I}_S$, since no power loss...

The Electrical Power System

• The usefulness of transformers lies in how it can be used to progressively DECREASE or INCREASE voltage... When transporting alot of power, HIGH voltage is needed to reduce power loss
• How power is DELIVERED to your house:
  

References

4.6 Electromagnetism
4.4 Conductivity, Kirchhoff's Laws and Power
4.0 Electrical Charge