Question

When to use left hand rule?

Answer 1

The left-hand rule is typically used in **electromagnetism** to determine the direction of force, magnetic field, or current in a system involving moving charges, magnetic fields, or currents. You’ll use it mainly for **motors** and **generators**.

Here’s how it works:

### **Left-Hand Rule for Force (Motor Effect)**:
When a current flows through a conductor placed in a magnetic field, it experiences a force. The **left-hand rule** helps to find the direction of this force.

1. **Point your thumb** in the direction of the current (I) — this is the direction the charges are moving through the conductor.
2. **Point your fingers** in the direction of the magnetic field (B).
3. The **direction your palm faces** will show the direction of the force (F) acting on the conductor.

This is used when you are working with devices like electric motors, where current interacts with a magnetic field to produce motion.

### **When to use the Left-Hand Rule**:
- **Electric Motors**: To find the direction of motion of a motor's armature when current flows through the coil inside a magnetic field.
- **Magnetic Force on a Moving Charge**: If a moving charge experiences a magnetic field, the left-hand rule can be used to determine the direction of the force on that charge.

### **Key Difference**:
The left-hand rule is specifically used for **motors** (where a current-carrying conductor experiences force due to a magnetic field). In contrast, the **right-hand rule** is generally used for generators and the magnetic field around a current.

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