How to Correctly Position an Ammeter to Measure Headlight Current?

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To correctly position an ammeter for measuring headlight current, it is essential to place it in series with the load. The manufacturer specifies that the 12V headlight draws 6A, but initial calculations show incorrect values of 120A for both circuits due to not accounting for the headlight's resistance. The resistance of the headlight must be considered to accurately measure the current. Circuit a is identified as the correct configuration for the ammeter measurement. Properly applying Ohm's law will yield the expected current reading.
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Homework Statement


The manufacturer of a 12V car headlight specifies it will draw a current of 6A. You would like to check this claim with an ammeter designed to measure currents up to 10A and having a resistance of 0.1 Ohms. Which of the two figures below represents a circuit where the ammeter correctly measures the current in the headlight?
a). How much current (in A) would flow in the ammeter for Circuit a?
b.)How much current (in A) would flow in the ammeter for Circuit b?

OA-Ammeter.jpg

Homework Equations


delta(V) = IR


The Attempt at a Solution



Circuit a should be the ammeter measurement
a.)I = 12/0.1 = 120
b.)I = 12/.01 = 120
 
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dasblack said:
delta(V) = IR
…
Circuit a should be the ammeter measurement
a.)I = 12/0.1 = 120
b.)I = 12/.01 = 120

Hi dasblack! :smile:

Yes, circuit a.

But you haven't used the resistance of the headlamp …

what should you assume it is (from the manufacturer's specification)? :wink:
 

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