A student measures a magnetic field at a distance from a straight wire carrying current

PHYSICS · Single correct · AP · Physics C: Electricity and Magnetism · Magnetic Fields and Electromagnetism · Magnetic Fields and Electromagnetism

Problem

A student measures a magnetic field

B_1

at a distance

r

from a straight wire carrying current

I

. What is the ratio

\dfrac{B_2}{B_1}

if the current is doubled and the distance is tripled? (a)

\dfrac{3}{2}

(b)

\dfrac{2}{9}

(c)

\dfrac{2}{3}

(d)

\dfrac{4}{3}