A long, straight, current-carrying wire runs from north to south. If you know the direction of the current, how can you determine the direction of the magnetic field?
a.
Grasp the wire in your right hand with the thumb in the direction of the current, the four fingers will curl in the direction of the magnetic field.
c.
Grasp the wire in your left hand with the thumb in the direction of the current, the four fingers will curl in the direction of the magnetic field.
b.
Grasp the wire in your left hand with the thumb opposite the direction of the current, the four fingers will curl in the direction of the magnetic field.
d.
Grasp the wire in your right hand with your thumb opposite the direction of the current, the four fingers will curl in the direction of the magnetic field.
The correct answer is a. Grasp the wire in your right hand with the thumb in the direction of the current, the four fingers will curl in the direction of the magnetic field.
To determine the direction of the magnetic field produced by a current-carrying wire, you can use the right-hand rule. This rule states that if you point your right thumb in the direction of the current, your curled fingers will indicate the direction of the magnetic field.
Imagine holding the wire vertically with your right hand, so that your thumb points upward (in the direction of the current). If you were to curl your fingers around the wire, they would curl in a clockwise direction. This curling of the fingers represents the direction of the magnetic field created by the current in the wire.
So, according to the right-hand rule, if you know the direction of the current in the wire, you can determine the direction of the magnetic field by grasping the wire with your right hand, pointing your thumb in the direction of the current, and observing the curling of your fingers. This matches option a: Grasp the wire in your right hand with the thumb in the direction of the current, the four fingers will curl in the direction of the magnetic field.