How Electricity Actually Works

TL;DR

Electric fields, not electrons, carry energy in circuits. When a switch is closed, the electric field travels at the speed of light, causing current to flow through the circuit and powering the load.

Transcript

I made a video about a gigantic circuit with light-second long wires that connect up to a light bulb, which is just one meter away from the battery and switch, and I asked you, after I closed the switch, how long will it take for us to get light from that light bulb? And my answer was 1/c seconds. - And his answer is wrong. - We would be able to co... Read More

Key Insights

• 🏑 The electric field, not the movement of electrons, is responsible for the transfer of energy in circuits.
• 🏑 Capacitors and inductors in distributed element models help capture the effects of electric fields and magnetic fields on the circuit behavior.
• 😚 Current flows through the circuit almost immediately after the switch is closed due to the propagation of the electric field.

Questions & Answers

Q: How does the electric field in a circuit cause current to flow?

The electric field, created by charges on the battery and surface charges in the wires, accelerates the free electrons in the circuit. These accelerated electrons transfer energy to the load through collisions with the lattice, causing current to flow.

Q: Can a current flow even if the circuit is not complete?

Yes, current can flow through the circuit even if it is not complete. The electric field from the modified surface charges travels at the speed of light and causes current to flow through the load. The circuit being complete or not does not affect the current flow.

Q: Why do we use voltage and current as the main quantities in circuit analysis?

Voltage and current are used as convenient macroscopic quantities in circuit analysis. They provide a simplified view of circuits, hiding the intricate details of electric fields and charges. However, understanding the role of electric fields is essential to grasp the underlying physics of circuits.

Q: How is the energy transferred in a circuit?

The energy in a circuit is carried by electric and magnetic fields, not by electrons. The changing electric fields create magnetic fields, and vice versa, leading to the propagation of energy through the circuit. The energy transfer occurs at the speed of light.

Summary & Key Takeaways

• When a switch is closed in a circuit, the electric field created by charges on the battery and surface charges in the wires propagates at the speed of light.

• Current flows through the circuit due to the electric field, not the movement of electrons. The electrons are guided by the electric field.

• The electric field transfers energy to the load, causing it to emit light almost immediately.