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Theory:

In the previous section, we did an activity to find the direction of the magnetic field associated with a current-carrying conductor.
 
In this session, we will learn a convenient way of finding the direction of the magnetic field associated with a current-carrying conductor.
 
Right-Hand Thumb rule:
Assume that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of the current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field, as shown in the figure. This is known as the right-hand thumb rule.
542px-Long-wire-right-hand-rule.svg.png
Right-Hand Thumb rule
  
If the current flow in an upward direction, then the direction of the field lines will be anticlockwise.
 
If the current flows in a downward direction, then the direction of the field lines will be clockwise.
 
This rule is also called Maxwell's corkscrew rule.
 
Maxwell's corkscrew rule:
Let us assume we drive a corkscrew in the current direction, then the corkscrew's direction is the direction of the magnetic field.
7.png
Maxwell's corkscrew rule
 
When we turn a corkscrew from right to left (clockwise), it goes into the cork. Then,
Current direction - downward,
Magnetic field direction - clockwise
  
What is a corkscrew?
 
It is a device for pulling corks from bottles, consisting of a spiral metal rod inserted into the cork and a handle that extracts it.
 
Summary:
 
Direction of current flowDirection of Magnetic field
Downwards (top to bottom)
Clockwise
Upwards (bottom to top)
Anticlockwise
Reference:
https://commons.wikimedia.org/wiki/File:Long-wire-right-hand-rule.svg;