E1OM.1 We can use Oersted\'s discovery to measure the cur- rent flowing in a wir
ID: 1873174 • Letter: E
Question
E1OM.1 We can use Oersted's discovery to measure the cur- rent flowing in a wire without having to break into the circuit to connect in an ammeter. Imagine that you have a compass sitting on a tabletop whose needle is pointing north, as shown in the left diagram below. We then bring a long, straight current-carrying wire oriented in the north- south direction down on top of the compass, as shown in the right diagram, so that the separation between the wire and the center of the compass needle is 0.40 cm. We then observe that the compass needle is deflected 15 to the left. Wire 15° Bearth Compass Assume that the horizontal part of the earth's magnetic field at our location has a magnitude of Berth 1-25 (a) What must be the direction of the magnetic field that the wire creates at the compass's center? Explain. (b) What is the direction of the current in the wire? (c) What is the magnitude of the current in amperes?Explanation / Answer
from the given data in the question
the needle deflects to teta = 15 deg to the left
now, since the wire is in the direciotn of the horizontal compoennt of earths magneitc field
a. the direction of magnetic field to the wire is to the left of the wire at the location of the center of the compass, as the magnetic field has to be to the left or to the right ( form right hand rule) and as the needle moves to the left, hence the force ius to the left, and hence magnetic field is to the left
b. hence direciton of current in the wire is from bottom to top
c. Given
Bwire/Bearth = tan(15)
Bwire = tan(15)*25*10^-6
also, Bwire = 2kI/0.4*10^-2
hence
I = 0.133974596 A
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