Questionable resistance pictures included

[dasblack]

Homework Statement

You would like to check if the battery voltage drops while it is supplying a current of 6A. You use a voltmeter designed to measure voltages up to 20V and having a resistance of 50,000 Ohms. Which of the two circuits below should be used?
a.) How much current (in A) would flow through the headlight for Circuit a?
b). How much current (in A) would flow through the headlight for Circuit b?

Homework Equations

delta(V) = IR

The Attempt at a Solution

Circuit a should be used because it has the least resistance.

a.) I = 12/50000 = 2.4e-4
b.) I = 12/50000 = 2.4e-4

 

[Carid]

Before putting the voltmeter into the circuit the current passing in the headlight is 6 amps.
What is the resistance of the headlight?
How does that compare to the resistance of the voltmeter?

The purpose of a voltmeter is to measure a voltage while actually disturbing that voltage as little as possible. Voltmeters are designed to draw as little current as possible.

Now consider which diagram is appropriate.

 

[thomate1]

The current flowing through the headlight in both circuits is the same because the resistance of the voltmeter is significantly higher than the resistance of the headlight. Therefore, the headlight can be considered a negligible resistance in comparison.