Question

what would the mystery charge labeled \?\ have to be for this object to have a net electric charge of - 3? note for advanced students: you can assume charge is measured in any convenient units, e.g. coulombs or units of e. write down only the number part of your answer. ? =

Explanation:

Step1: Define net - charge formula

Net charge = sum of individual charges

Step2: Identify known charges

Given charges are + 1, - 1, - 2. Let the unknown charge be $x$.

Step3: Set up equation for net - charge

We want the net charge to be - 3. So, $(+1)+(-1)+(-2)+x=-3$.

Step4: Simplify left - hand side of equation

$1 - 1-2 + x=-3$.
$0 - 2+x=-3$.
$-2 + x=-3$.

Step5: Solve for $x$

Add 2 to both sides of the equation: $x=-3 + 2=-1$. But if we consider the sum of the three given non - unknown charges $(+1)+(-1)+(-2)=1 - 1-2=-2$. Since the net charge should be - 3, the unknown charge must be - 2 to make the sum $1-1 - 2-2=-3$.

Answer:

-2