I need help

In studying the cross section of a straight current carrying wire, you notice that the magnetic
field lines run counter-clockwise. What is the direction of the current in the wire and how do you
know?
2. You are looking into a current carrying solenoid and notice that the compass needle indicates
that you are at the South end of the magnetic field. What is the direction of the current in the coil
and how do you know?

Use right hand rule.

To determine the direction of current in these scenarios, you can use the right-hand rule for a straight wire and the right-hand thumb rule for a current-carrying coil.

1. For a straight wire:
The right-hand rule for a straight wire states that if you grip the wire with your right hand, with your thumb pointing in the direction of the current, then your fingers will naturally curl in the direction of the magnetic field lines. In this case, you notice that the magnetic field lines run counter-clockwise.

By applying the right-hand rule, you would conclude that the current must be flowing in the opposite direction, or clockwise. So, the direction of the current in the wire is clockwise.

2. For a current-carrying solenoid:
The right-hand thumb rule for a current-carrying coil states that if you point your right thumb in the direction of the current, your fingers will wrap around the coil following the direction of the magnetic field lines. In this case, you find that the compass needle indicates you are at the South end of the magnetic field.

To use the right-hand thumb rule, you would consider yourself standing in the same position as the compass needle. With the South end of the magnetic field pointing towards you, curl your fingers in the same direction as the field lines.

As a result, your thumb will naturally point in the direction of the current. If your thumb points downwards in this scenario, then the direction of the current in the coil is downward.