In a conventional cheap flashlight, a straight copper strip runs along the tube
ID: 2061577 • Letter: I
Question
In a conventional cheap flashlight, a straight copper strip runs along the tube of the flashlight to connect the bulb to the negative terminal of the battery at the bottom of the tube.If this strip carries a current of 0.57 A while you’re holding the flashlight, what is the magnitude of the magnetic field at the surface of your hand, 0.31 cm from the strip? (You can treat the strip as a long, thin, straight wire.)
Express your answer to two significant figures with the appropriate units.
B =
How does your answer compare to the earth’s magnetic field?
These values has the same order.
This value is significantly larger than the earth’s magnetic field.
This value is significantly smaller than the earth’s magnetic field.
Explanation / Answer
The formula for magnetic field around a current carrying wire is
B = oI/2r
B = (4 X 10-7)(.57)/(2)(3.1 X 10-3)
B = 3.67 X 10-5 T or, with two significant figures, 3.7 X 10-5 T or 37T
Generally speaking, this is almost identical to the earths magnetic field, but that field does vary. Please see the explanation I gave to you in the other problem I solved for you regarding the values.
However, since we are still talking of an order of magnitude of 10-5 T, the order of magnitude is the same