# Advice 1: How to determine the direction of the Lorentz force

The force of Lorentz defines the intensity of an electric field on a point charge. In some cases, it meant the force with which the charge q that moves with velocity V, the magnetic field acts, in other meaning the net impact of electric and magnetic fields.
Instruction
1
To determine the direction of force of Lorentz, was established the rule of thumb of the left hand. It's easy to remember because the direction is determined by using your fingers. Open palm of left hand and straighten all the fingers. Thumb fold back to an angle of 90 degrees relative to all other fingers in the same plane as the palm.
2
Imagine that four fingers of the palm that you hold together, indicate the direction of the velocity of the charge if it is positive, or opposite to the velocity directionif the charge is negative.
3
The magnetic induction vector which is always directed perpendicular to the velocity, will thus enter the hand. Now look where the thumb points is the direction of force of Lorentz.
4
The force of Lorentz can be zero and not have a vector component. This happens in the case when the trajectory of a charged particle is located parallel to the magnetic field lines. In this case, the particle has a straight trajectory and constant speed. The force of Lorentz does not affect the motion of the particle, because in this case she is absent.
5
In the simplest case a charged particle has a trajectory perpendicular to the magnetic field lines. Then the force of Lorentz creates a centripetal acceleration, causing a charged particle to move in a circle.
Note
The Lorentz force was opened in 1892, Hendrik Lorentz, physicist from Holland. Today it is quite often used in various electric appliances, the effect of which depends on the trajectory of the moving electrons. For example, a cathode-ray tube in TVs and monitors. Various accelerators, accelerates charged particles to enormous velocities by the Lorentz force asking their orbits of movement.
A special case of the Lorentz force is the ampere force. Its direction is calculated according to the left-hand rule.

# Advice 2 : How to determine the direction of magnetic induction

Magnetic induction is a vector quantity and therefore also the absolute value is characterized by a direction. To find it, you need to find the pole of a permanent magnet or the direction of the current which produces a magnetic field.
You will need
• - the reference magnet;
• - current source;
• - the right thumb;
• - straight conductor;
• - coil, coil of wire, a solenoid.
Instruction
1
Determine the direction of the vector of magnetic induction of the permanent magnet. To do this, locate North and South pole. Typically the North pole of the magnet is blue and South is red. If the poles of the magnet is unknown, take the reference magnet and move its North pole towards the unknown. The one end that is attracted to the North pole of the reference magnet will be South pole of the magnet, the induction field is measured. Lines of magnetic induction leave the North pole and enter the South pole. Vector in every point of the line going in the direction of the tangent line.
2
Determine the direction of the vector of magnetic induction of a straight conductor with a current. Current flows from the positive pole of the source to the negative. Take the corkscrew which is screwed when rotating clockwise, it is called the right. Start to twist it in the direction where a current flows from the conductor. Rotation of the handle will indicate the direction of closed circular lines of magnetic induction. The vector of magnetic induction in this case will be tangent to the circle.
3
Find the direction of the magnetic field of the coil with current, the coil or solenoid. To do this, connect the conductor to the current source. Take the right thumb and rotate his arm in the direction of the current going in to the turns from the positive pole of the current source to the negative. Translational movement of the rod of thumb will show the direction of the magnetic field lines. For example, if the handle of the corkscrew rotates in the direction of the current is counterclockwise (to the left), he, twisting, steadily moving toward the observer. Therefore, the magnetic field lines are directed also in the direction of the observer. Inside the coil, the coil or solenoid the magnetic field lines are straight, the direction and absolute value coincide with the vector of magnetic induction.