Many people intuitively think that electric devices with heating elements have a high resistance, i.e., that they get heated due to higher resistance of the conductor element. In the university days, one of our friends from Electrical Engineering (Syed Atif Shah) told us that it was not the case and that devices with higher power rating actually have a low-resistance. The formula for electric power is P = I*I*R where P is for power, I for current and R stands for resistance. Current is squared and therefore it plays the major role. I decided to put this theory to the test and find out for myself. There are many electrical devices lying around and one can easily find out.
The electric supply voltage and frequency are the same for all cases. The power rating is read from the manufacturer labels and resistance is measured with a multimeter. Ideally the current should also have been measured with an inductive ampere gauge but that instrument was not available.
This is a coffee-maker of 2000-2400 Watts for 220-240 Volts electric supply of 50-60 Hz frequency. It had a resistance of 27 ohms. It clearly shows that its power is due to high amount of current.
A 1000 Watts water heating coil. It had a resistance of 52.5 ohms as shown below. Again low-resistance, high-current is verified.
Our electric stove of around 1300-1500 Watts gave a resistance of 39.6 ohms at one fixed position of the switch. Obviously the resistance of electric wires was also included but its negligible compared to the heating element itself.
The electric iron of almost 1100 Watts gave a resitance of 69.8 ohms at one fixed position of the control knob. Therefore it is also a case of low-resistance and high-current.
Now something with a lower power rating. A 75 Watts electric bulb had a resistance of almost 57 ohms. This points to lower power, higher resistance case, keeping the same supply voltage.
Electrical guys, do add your observations as it is your field.
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