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## Homework Statement

In a lightning bolt, 13 C of charge flows in a time of 1.5 10-3 s. Assuming that the lightning bolt can be represented as a long, straight line of current, what is the magnitude of the magnetic field at a distance of 20 m from the bolt?

## Homework Equations

B = mu(I)/2(pi)r

## The Attempt at a Solution

Ok, the current is the change of charge over time, thus should be equal to 13/(1.5X10^-3), or 8666.66 A. The only other variable in in the equation would be "r", or radius, which should be the distance from the bolt (20 m).

So, by plugging 8666.66 into the "I" variable and plugging 20 into the "r" variable, my equation yields B to equal ".3421 T".

According to the answer key to this homework assignment, the value I should be getting for B is "8.67e-05 T". Am I using the incorrect equation?

Thanks,

-Will