Difference between electrical resistance and heating resistant
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When we lower the resistance R we will see more current and thus more heat.
That's counter-intuitive to the general observation that "if it's easier for electricity to flow through a wire then it loses less energy so gives off less heat.
Here's what an electronics forum discussion explained: two things can be true at once:
Any given resistor can dissipate the same amount of power. It just depends on the product of voltage and current
P = V x I or Power = Volts x Amps
Since V = I x R and I = V / R the expression for the power can be rewritten as
P = V x (V / R) or
P = V2 / R
or as
P = (I x R) x I or
P = I2 x R
The first equation (P = V x I ) suggests that a higher resistance would be better [to obtain a higher current]
while the second (P = I2 x R ) shows that a lower resistance would be better [to obtain a higher voltage or less voltage drop]
So it depends on the application if it is easier to generate a higher current or a higher voltage and you have to choose the resistor
If the electrical resistance in a circuit is very low, electrons can move right through without losing much energy [in the form of heat], whereas if the resistance is high the electrons meet resistance, lose energy, and that lost energy is given off as heat. (P=VI & V= IR).
But we also see that P=VI is not a measure of heat, it's a measure of power.
The heat given off by a resistor is I 2 R
When we keep the same voltage (24VAC on a thermostat heat anticipator circuit) if we keep the same resistance (Ohms) then the heat produced is given by (V/R)2 (R) = V2 R.
Dividing the square of the voltage by the circuit resistance means that as we lower the resistance we see more heat produced.
Why does this make sense for the little heater in the thermostat's heat anticipator? Because for that circuit, the little heater wire is the only thing in the circuit. Nothing else is limiting current flow through that little wire, so it gets warm - or even hot.
That's counter-intuitive to the general observation that "if it's easier for electricity to flow through a wire then it loses less energy so gives off less heat.
Here's what an electronics forum discussion explained: two things can be true at once:
Any given resistor can dissipate the same amount of power. It just depends on the product of voltage and current
P = V x I or Power = Volts x Amps
Since V = I x R and I = V / R the expression for the power can be rewritten as
P = V x (V / R) or
P = V2 / R
or as
P = (I x R) x I or
P = I2 x R
The first equation (P = V x I ) suggests that a higher resistance would be better [to obtain a higher current]
while the second (P = I2 x R ) shows that a lower resistance would be better [to obtain a higher voltage or less voltage drop]
So it depends on the application if it is easier to generate a higher current or a higher voltage and you have to choose the resistor
If the electrical resistance in a circuit is very low, electrons can move right through without losing much energy [in the form of heat], whereas if the resistance is high the electrons meet resistance, lose energy, and that lost energy is given off as heat. (P=VI & V= IR).
But we also see that P=VI is not a measure of heat, it's a measure of power.
The heat given off by a resistor is I 2 R
When we keep the same voltage (24VAC on a thermostat heat anticipator circuit) if we keep the same resistance (Ohms) then the heat produced is given by (V/R)2 (R) = V2 R.
Dividing the square of the voltage by the circuit resistance means that as we lower the resistance we see more heat produced.
Why does this make sense for the little heater in the thermostat's heat anticipator? Because for that circuit, the little heater wire is the only thing in the circuit. Nothing else is limiting current flow through that little wire, so it gets warm - or even hot.
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