Question

Which of the following are voltage sources?

Ohm's law
resistance
electric charge
batteries and wall sockets

Answer 1

batteries and wall sockets )

Answer 2

batteries

Answer 3

Batteries and Wall sockets

Answer 4

Batteries and wall sockets

Answer 5

for a electrical element to be a voltage source the voltage across the element should not vary with current flowing through it...ohm's law or resistance or electric charge..can't be electrical elements but resistor can be and capacitor can be..so voltage across the resistor v=ir
voltage clearly depends on i so can't be the voltage source
and capacitor voltage drop=Ldi/dt now it also can't be a voltage source..
but if i say batteries then bingo voltage drop is independent of current flowing through them(if we ignore internal resistance of battery)...hence batteries are voltage sources...
hope it helps...:)