How would an interior light stay on if you pulled out the fuse for it

[Hugomartin]

Was watching a youtube guy diagnose a 'short'. I know in residential wiring AC if you trip a fuse that circuit does not work.....

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aound midway in the video he pulls the fuse for the light but its still on and drawing current.... I thought the fuse socket was an interrupter of the hot leg or positive wire? How is the hot wire getting to turn on the light

 

[mibars]

He pulls the fuse in order to measure current. He breaks the circuit removing the fuse then connects is back together with a multimeter instead of a fuse. Multimeter set to measring current has a resistance close to zero ohm.

 

[mibars]

My $0.02: The guy is using 20 A range for that test. It is good for initial check, but far for good for measuring actual values.
For measuring anything (electrical, distances, temperatures, whatever) you want to use as much of the measuring device range as possible. Measuring milliamps on a 20 A range adds a lot of uncertainty of measurement.

Say you measure 100 mA. Your multimeter has a 200 mA range and a 20 A range and on both ranges it has an example tolerance of 1% of measured value plus 1% of the range.

On a 100 mA range you'd get a tolerance of 1 mA (1% od 100 mA) + 2 mA (1% of your range 200 mA. So when your multimeter displays 100 mA it means anything between 97 to 103 mA. Good enough for most stuff even with such high tolerances I've used in the example.

However if you use 20 A range then you have a tolerance of 0.001 A (1% of 100 mA) + 0.2 A (1% of 20 A). So when your multimeter displays 0.1 A you may be actually measuring anything between MINUS 0.101 A to 0.301 A. That's basically a meaningless measurement.

 

[Hugomartin]

He pulls the fuse in order to measure current. He breaks the circuit removing the fuse then connects is back together with a multimeter instead of a fuse. Multimeter set to measring current has a resistance close to zero ohm.

Ok i was assuming the light stayed on after he pulled the fuse thanks for clearing that up . I have another question how does this test light turn on when its connected to positive battery terminal and the positive battery wire. He mentions an interior light is switched on
Does the test light have a built in ground or does the test light obtain a ground through the path of the positive wire?

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