A current-carrying straight wire is held in exactly vertical position. If the current passes through this wire in the vertically upward direction, what is the direction of magnetic field produced by it? Name the rule used to find the direction of magnetic field.

It is given that the current-carrying straight wire is held in the vertical position. If current passes through this wire in a vertically upward direction, the magnetic field produced by it will be in the anticlockwise direction.

Maxwell's right-hand thumb rule is used to find the direction of the magnetic field. 

Explanation

According to Maxwell’s right-hand thumb rule, when a current-carrying conductor is held in the right hand so that our thumb points in the direction of the current, and the fingers that have wrapped the conductor gives the direction of the magnetic field lines around the wire.

When thumb points upwards, the wrapped fingers are anticlockwise. Hence, the direction of the magnetic field is anticlockwise. While when thumb points downwards, the wrapped fingers are clockwise. Hence, the direction of the magnetic field is clockwise.