[Physics] Does a resistor absorb and dissipate energy or just regulate the charge flow

electrical-resistanceelectricity

I've this doubt regarding resistor: suppose I make a simple circuit with a power generator of 3 Volts and 1 Ampere and a resistor of $10 k\Omega$ I know from Ohm law that the current flow $i$ is:

$$I=\frac{V}{R}=\frac{3 V }{10000 \Omega}=0.3mA$$

So if I place my multimeter in series after the resistor I can measure exactly that current , and if I place the probe in parallel I can measure $3V$ so in this case I think that the resistor regulate the charge flow to 0.3 mA but in fact is the whole circuit to dissipate this current after the resistor regulated it, because I can see it passing through the multimeter ( and indeed 0.7 Amp give by the generator are not dissipated).

Shorting out the circuit with no resistance attached I can't measure an increase of temperature (I think because I'm not working with high power) but if a use a smaller resistor (e.g. $2 \Omega$) I can fell it getting hot so I infer that a smaller resistor dissipate more energy (in this case I've $1 Amp$ passing through it) but I think that this is no more a good charge regulator because it dissipate a lot of energy through Joule effect.
So I don't know if exists materials that can be a good "charge regulator" (e.g. a good resistor) and material that can be good "energy dissipator" (e.g. good heater). I've tried to make my homemade analogous resistor cutting $3,5 cm$ of a kanthal wire with a resistance of $57 \Omega / m$ but I can't measure correctly if this dissipate better the energy. Can anyone tell me what really do a resistor?

Best Answer

The heat generated is the wattage dissipated, namely $W = VI$, so if the resistance is lower, the current will be higher, and if the voltage remains the same, you get more heat.

If you short out the battery (provide a very low-value resistor) then the other resistance in the circuit will take the heat, namely the battery itself, and the voltage across the short circuit will be zero. This is a good way to burn out a battery.

EDIT: OK, you're saying it is counter-intuitive that more resistance means less heat. Let me try to explain it. First, let's assume the voltage source has very low internal resistance compared to the resistor you are experimenting with, like, say, a 12-volt car battery.

Now, you put your resistor R of, say, 1 ohm across the poles of the car battery. So 12 amps will flow, so 12*12 watts of heat come off. 144 watts, that's a lot of heat. (In fact, you should probably be using big light bulbs instead of little resistors.)

Now, you take two resistors R and tie them in parallel. How much resistance do they have? R/2, because 12 amps will flow through each one, for 24 amps total. (R = V/I = 12/24 = 1/2 ohm) Each resistor sees 12 volts and 12 amps for 144 watts, but what does the pair of them see? 144 watts in each one, so 288 watts together. So by cutting the resistance in half, you doubled the heat (assuming the source has low internal resistance).