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Have two different loads on two circuits, the first circuit is running at 3.3V, second is 5V. Those two loads draw exactly 100mA on each. The question is, does those two circuits have the same amount of electrons transfered in the same period of time?

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Short answer, yes. Both the circuits have same amount of electrons transferred in the same period of time.

Theory behind it:

Current is the rate of flow of charge and voltage is the amount of work done in moving that charge from some point to another point.

Now since both the circuits are drawing 100mA of current that means both the circuits have same no of electrons flowing at any particular point. But different amount of work needs to be done to achieve that same flow and hence different amount of power in both the circuits (P=VI)

A good analogy is a water, so current (rate of flow) is a flow of water where as the voltage is analogous to pressure in the system that will cause the water to flow (ie current).

So both the systems have the same amount of water flowing in given time period but one system needs to work more than the other to achieve the same rate of flow.

That means 5V circuit is putting more amount of work to maintain 100mA in circuit compared to 3.3V circuit.

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  • \$\begingroup\$ perfect explanation to clear my confusion, thank you :) \$\endgroup\$ – Huy.PhamNhu Jul 22 '17 at 5:36
  • \$\begingroup\$ @Mayank Why would it be more work for 5V? Isn't 5V stronger than 3.3V? It makes it looks like it needs less work because 5 volts is "stronger." \$\endgroup\$ – johnny Sep 25 '18 at 19:19
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Yes, the same number of electrons is being transferred per unit of time in each case.

Nonetheless, more power is being delivered to the load in the case with higher voltage.

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