Eddy currents are circular currents induced in a conductor when it is exposed to a changing magnetic field. These currents create their own magnetic fields and can lead to various practical effects. Here are two common uses of eddy currents:
### 1. **Magnetic Braking**
Eddy currents are widely used in **magnetic braking systems** found in electric trains, roller coasters, and other transportation vehicles.
#### How it works:
- When a conductor (usually made of metal) moves through a magnetic field, or when a magnetic field changes around a stationary conductor, eddy currents are induced in the conductor.
- These currents generate their own magnetic fields, which oppose the motion of the conductor due to **Lenz's Law**.
- This opposition creates a force that resists the motion, thus slowing the object down without any physical contact or friction.
#### Example:
- In **trains** or **elevators**, when they need to stop, the magnetic braking system induces eddy currents in a metal disc or wheel. The resistance from these currents provides a smooth, non-wearing brake effect.
### 2. **Induction Heating**
Eddy currents are also used in **induction heating**, where they are employed to heat conductive materials without direct contact. This is commonly used in industrial processes like metal hardening, cooking appliances, or welding.
#### How it works:
- A changing magnetic field from a coil induces eddy currents in the material being heated (usually a metal).
- These eddy currents encounter electrical resistance in the material, causing it to heat up due to **Joule heating** (also called resistive heating).
#### Example:
- In **induction cooktops**, a magnetic field is generated by the coils under the cooking surface. When a metal pot is placed on the cooktop, eddy currents are induced in the pot, causing it to heat up quickly and cook the food efficiently.
These are just two applications, but eddy currents have many other practical uses, such as in metal detectors, electric meters, and nondestructive testing.