Energy does NOT flow inside the wire..
(Energy flows in the electromagnetic field around the wire.)
Energy does NOT flow inside the wire..
(Energy flows in the electromagnetic field around the wire.)
π Energy does NOT flow inside the wire.
π Energy flows in the electromagnetic field around the wire.
The wire is not a pipe carrying energy
The wire is a guide for fields
The energy travels in space, not in the copper
The wire is like a rail.
The electromagnetic field is the train.
We are taught:
Electrons move β carry energy β power the load
But this breaks down:
Electrons drift extremely slowly (mm/s or less)
Yet the light turns on almost instantly
π So electrons cannot be delivering energy physically from source to load.
Inside the wire:
Electrons move randomly at ~1,000,000 m/s (thermal velocity)
But in all directions equally β cancels out
Then:
A tiny bias (drift velocity) is added by voltage
This drift is extremely slow
Crowd running randomly in a station = thermal motion
Slight lean in one direction = current
π Current is just a tiny imbalance, not bulk transport of energy
Common explanation:
Push one electron β pushes next β chain reaction
βοΈ True: signal propagates fast (~2/3 speed of light)
β Misleading: suggests energy flows through electrons
If electrons are everywhere in the loopβ¦
π How does energy know to go only from battery β bulb?
Maxwellβs equations showed:
Electric fields create magnetic fields
Magnetic fields create electric fields
π This produces self-propagating waves
Energy can travel through empty space
No medium required
π This is electromagnetic radiationβand also what happens in circuits
Physicist John Henry Poynting defined:
π Energy flow = cross product of electric and magnetic fields
Direction = where energy flows
Magnitude = how much energy per area
This is called the Poynting vector
Around a current-carrying wire:
Along the wire (drives current)
Radially outward (due to surface charges)
Circles around the wire
π E Γ B = energy flow
β‘οΈ Energy flows from space INTO the wire
Not along it.
At the bulb:
Energy comes from all directions
Flows inward from surrounding space
Gets converted into:
Heat
Light
π The wire is not delivering energy
π The field is feeding the load
Very important (often ignored):
Tiny charges build up on the surface of the wire
They are not uniform
They create a gradient along the wire
Shape the electric field inside AND outside the wire
Control where energy flows
π Without them:
No structured field
No controlled energy transfer
Good question:
π βIf energy flows in space, why use wires?β
Because:
Wire β allows current
Current β creates magnetic field
Electric + Magnetic fields β create energy flow
Without wire:
β No current
β No magnetic field
β No Poynting vector
β No usable energy flow
Sequence:
Electric field changes
Change propagates at ~speed of light
Field reaches bulb almost instantly (~nanoseconds)
Energy starts flowing immediately
Light appears before electrons complete the loop
Full brightness takes longer (steady state)
π Energy arrives via the field, not electrons
Field propagates through space directly
Fields stabilize
Continuous energy flow maintained
In a coax cable:
Inner conductor + outer shield
Field exists only between them
π Energy flows entirely in the empty space between conductors
Not in the metal.
Engineering a cable = engineering the space where the field lives
In some systems (charge + magnet):
Energy can flow in closed loops
No work is being done
But energy still βmovesβ
π This energy carries real momentum
Even angular momentum
Measurable in experiments
Electrons carry energy through wire
Battery creates electric field
Current creates magnetic field
Fields combine β energy flow
Energy travels in space
Wire guides and shapes the field
Energy in circuits flows in the electromagnetic field around the wires, guided by themβnot inside them.
Even though energy flows in the field:
Wires still matter A LOT:
Cross-section β current handling
Insulation β voltage safety
Mechanical strength β durability
π The wire doesnβt carry the energy
π But it controls how the energy flows