8.4 Using Electromagnets Flashcards
How do we use magnets in x-rays?
Radiographers operating X-ray prolonged exposure to them, as they can damage cells. The machine uses a high-voltage circuit, which is turned on and off using a relay.
What are relays? How do they work?
A relay uses a small current to switch on a dangerous circuit, using a simple reed switch made of two pieces of magnetic material called reeds. When a coil of wire is passed through, the reeds are magnetized, attracting each other and touching. If the reeds are part of another circuit, current flows in the second circuit.
Give an example where a relay is used.
A relay circuit activates the starter motor in a car, generating a small current that magnetizes the iron armature, attracting it towards the car’s contacts, thus starting the car and completing the starter motor circuit.
How do we use magnets in fire doors?
Fire doors in large buildings prevent fires from spreading. If there’s no fire, an electromagnet coil on the door charges, attracting an iron. This holds the door open, allowing easy passage. When a fire alarm is triggered, the circuit is broken, causing the door to close.
How do we use magnets in medicine?
MRI scanners use strong magnets to produce intense magnetic fields, providing safe, painless, and detailed images. They can reveal body structures and organ function without cutting the patient open. However, they are expensive and require patient rest.
