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# The Motor Effect and Fleming's Left Hand Rule

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## The Motor Effect and Fleming's Left Hand Rule

If two magnetic fields combine, a force is exerted. One magnet exerts a force (attractive or repulsive) on the other.

**Look at these two fields:**

The strong field behind the wire pushes it upwards as shown.

This effect allows us to turn **electrical energy into kinetic energy.** We call it the **motor effect.**

**The size of the force can be increased by:**

- Increasing the magnetic field strength;
- Increasing the length of the wire in the field;
- Increasing the current in the wire.

**F = B I L**

*Where:*

**F** = Force on the wire (N)

**I** = current (A)

**B** = magnetic field strength (T)

**L** = length of the wire (m)

** Note:** The angle between the current and the magnetic field must be greater than zero for a force to be produced. The greatest effect is when the angle is 90º. So if the wire and the conductor are not perpendicular to each other we must use:

**F = B I L sin θ**

** Note:** The angle is measured between the field direction and the conductor.

To work out the **direction** of force experienced we use **Fleming's Left Hand Rule.**

- Your
**first**finger points in the**direction of the magnetic field**(North to South). - Your
**second**finger points in the**direction of conventional current**(positive to negative). - Your
**thumb**points in the direction of the**thrust or force**on the conductor.

*Remember direction is vital!!!*