GCSE PHYSICS - MAGNETISM AND ELECTROMAG - LESSON 13 - left hand rule

Understanding the Motor Effect and Left-Hand Rule

Introduction to the Motor Effect

• The lesson continues exploring the motor effect, focusing on determining the direction of force on a current-carrying conductor in a magnetic field.

• Previous discussions involved complex interactions between magnetic fields from permanent magnets and those produced by electric currents.

The Left-Hand Rule Explained

• The left-hand rule simplifies understanding force direction:

• Thumb = Direction of motion (force)

• First finger = Direction of magnetic field

• Second finger = Direction of conventional current

• To apply this rule, position your hand correctly and adjust until all directions align properly.

Example Scenario with Current and Magnetic Field

• In an example, current flows through a conductor moving along parallel rods; the direction is established as entering from one side.

• The magnetic field is defined as running from north to south based on magnet orientation.

Determining Force Direction Using the Left-Hand Rule

• With fingers positioned according to the left-hand rule:

• First finger points up (magnetic field).

• Second finger points into the screen (current).

• Thumb indicates that force acts to the right.

• This demonstrates how to find out that the conductor moves towards the right under these conditions.

Changing Magnetic Poles and Its Effects

• When reversing magnet poles while keeping current direction constant:

• First finger now points down (new magnetic field direction).

• Second finger remains pointing into the screen (current).