# Why electric devices do not draw more current than they need?

Tv set is an example You are supplied with 10 amperes Your tv needs 2 ampere Why can not your tv draw current more than 2 amper? If you say because ohm law , this law say that resistance resist current flow This mean the resistor of your tv set will permit flow of only 2 ampers The remaining which is 8 amperes will be prevented by resistor and converted to heat So all the 10 should be consumed by the tv set The tv is an example My question is more general Why the devices does not draw all the available current?

phinds
Gold Member
Tv set is an example You are supplied with 10 amperes Your tv needs 2 ampere Why can not your tv draw current more than 2 amper? If you say because ohm law , this law say that resistance resist current flow This mean the resistor of your tv set will permit flow of only 2 ampers The remaining which is 8 amperes will be prevented by resistor and converted to heat So all the 10 should be consumed by the tv set The tv is an example My question is more general Why the devices does not draw all the available current?
You misunderstand completely. You are NOT "supplying" 10 amps, you are supplying some voltage. The TV (or anything hooked up to an electrical power source) draws exactly as much current as it needs and there is no waste anywhere.

anorlunda
Staff Emeritus
Why do you think that the 10 amps comes, even if your devices don't use it? It doesn't work that way. The devices in your house draw the power they need from the grid. Power not used by the loads is never generated and never sent on the grid.

https://www.physicsforums.com/insights/what-happens-when-you-flip-the-light-switch/

russ_watters
Mentor
The remaining which is 8 amperes will be prevented by resistor and converted to heat
Amps are a unit of charge flow. Physically, it is a bunch of electrons. Electrons don't get converted to heat.

Apply a little critical thinking here. if a megawatt nuclear power plant can supply thousands and thousands of amperes at 120V, do you think that a single TV, when connected, will consume it all?

Averagesupernova
PhysicoRaj
Gold Member
A water tank contains of gallons of water (charge). The height at which it's placed is the pressure (voltage). The diameter of the outlet pipe(conductance) controls the flow rate (current). Now your resistance being the reciprocal of conductance, analyse how the flow rate (current) varies as you vary the diameter (resistance) as in a tap. You won't get all the water flowing in it at once, only the amount of water that can pass through the given diameter and at given pressure constitutes the flow.
So holds I=V/R.