How can a resistor have voltage?
a resistor can not have voltage per se. but a resistance traversed by a current will undergo a voltage drop. According to the law of the Ohm, the passage of a current in a resistance will generate a voltage across the resistance.
Distinguish the applied voltage from the voltage drop.
The voltage drop is the voltage measured at both ends of the resistor when it is installed in series in the electrical circuit. when the resistor is connected in parallel with the power source and this power source is considered a constant voltage source, we apply a voltage to the resistor.
it is difficult to make this difference in the case where a battery is connected to the resistor because the battery has an internal resistance and the voltage on the resistor can be considered as a voltage drop, or if you ignore the internal resistance (each time that the internal resistance is considerably more resistance of the resistor), then you can call it an applied voltage.
There may be a voltage drop, which is a totally different thing. what this means is that there is a current flowing through it from an outside source. like a battery. the resistance resists the current flow.
it takes some pressure to sink anything. water flows into a pipe because it is forced into it, usually by a pump. in the case where there is electric current, the battery in this thought is the pump. the resistance is a narrowing of a pipe.
If you have a 3 inch diameter pipe, connected to a 1/2 inch diameter pipe, then another 3 inches, the 1/2 inch pipe is the resistance. water will not flow as easily as 3-inch pipes. he resists the flow. the pressure measured on the side of the pump will be higher than the other. this pressure difference is a pressure drop.
By extending the idea, the narrowing of the path of the electrons causes a voltage drop across the resistor.
a resistance alone can not create or generate anything. if it could, we would probably have very serious problems: most parts of your body have resistance and could serve as resistors with resistance values ranging from hundreds of ohms to hundreds of megohms.
to present a voltage, a resistance must be crossed by a current. the amount of current and resistance of the resistor would determine the voltage across it. the mechanism is quite simple: the current is measured in charge (in counting electrons) passing a point in a circuit during a given period, the standard unit of measure being a coulomb of electrons per second. for a resistance of 1ohm, this would cause a voltage of 1v.
when the resistor is in a circuit with other resistors, the voltage comes from the source, whether it is a constant or constant voltage, the source will produce a voltage and the resulting current will be moderated by the total resistance of the circuit, or source produce a voltage suitable for maintaining a constant current in response to the changing resistance of the circuit.
in both cases, regardless of the voltage raised by the source, falls into the circuit, and each resistance drops a portion of this voltage proportional to its resistance to the total resistance. the current flowing through the whole circuit is the same at every point of the circuit, and a by-product of this current and the resistance of the resistor will produce the voltage it drops.
If this sounds like two competing ways of determining the tension of each resistance, you are right, because the two are absolutely bound together by Ohm’s law. where it becomes interesting is if one of the resistors is variable (as in a rheostat or an active element that controls the flow of current). In these cases, the resistance in the variable resistor controls the total resistance, thus modifying the current of the circuit and thus modifying the voltage on the purely resistive components, it is from this action that the amplification occurs.