Electromagnets
Year 8 ⚡ Electricity & Magnetism Describe solenoids, the factors affecting electromagnet strength, and uses.
🔌 Magnetic Effect of Current
When electric current flows through a wire, it creates a magnetic field around it. This is called the magnetic effect of current (or Oersted's discovery, 1820).
| 🔌 Configuration | 🧲 Magnetic field shape |
|---|---|
| Straight wire | Concentric circles around the wire |
| Circular loop | Field passes through the loop |
| Solenoid (coil) | Like a bar magnet (N and S poles) |
🧲 Solenoids and Iron Cores
A solenoid is a coil of wire. When current flows, it produces a magnetic field similar to a bar magnet. Adding a soft iron core makes it much stronger.
↑ Current (I) → ↑ Magnetic field strength
↑ Number of turns (N) → ↑ Magnetic field strength
Adding soft iron core → dramatically ↑ strength
⚙️ Uses of Electromagnets
Electromagnets have countless applications in technology!
| ⚙️ Application | 📝 How it uses an electromagnet |
|---|---|
| 🏗️ Scrapyard crane | Powerful magnet lifts steel cars; switch off to release |
| 🔔 Electric bell | Electromagnet attracts clapper repeatedly as current pulses |
| 🔊 Loudspeaker | Varying current moves cone to produce sound waves |
| 🚂 Maglev trains | Electromagnets levitate and propel the train |
| 🏥 MRI scanner | Very strong superconducting electromagnets map body tissues |
| ⚡ Relay switch | Small current controls large current safely |
Calculate the force on a current-carrying conductor in a magnetic field: F = BIL