Can anyone offer suggestions as to where I am going wrong please?
In my circuit (diagram below) the system voltage is 12.03 V and the lamp resistance is 2.9 ohms (measured with power disconnected through circuit). I was expecting to measure a current of 4.1 Amps (12.03/2.9 = 4.14)
However the DMM ammeter reads 0.450 A DC (positive lead to positive side of circuit). Screenshot below.
This doesn't tally with Ohm's law so I suspect that I am doing something wrong rather than Mr Ohm!
Thanks in advance for any help (first post here)
thanks for you comments. It appears then, that one cannot test for actual operation resistance from cold - I take it then one would need to operate circuit for some time, then disconnect power and then test resistance to gain a true reading. Haven't seen a mention of this real world scenario when reading about ohms law!
Once again thanks - off to re-test! N
Reply to all again. Re-tested. Voltage has dropped to 11.5 Closed the circuit and left it for 5 mins to heat up, tested current again, now showing as 1.74Amps. Took battery lead off and quickly tested circuit ohms and they momentarily showed a peak of 9-10ohms before quickly falling away (as bulb temp drops). So expectation might be 11.5v/1.74A=6ohms - something much nearer. I was (naively?) imagining this was all rather simpler than the real world appear to show! Thank you all - i have adjusted my expectations accordingly