magnetism - electromagnetic devices

Question 1

why is it dangerous to use a switch to turn on and off a high voltage appliance?

Answer 1

sparking + electrocution

Question 2

what do we use to turn on and off a high voltage appliance? explain it

Answer 2

a relay. this contains 2 separate circuits. a low voltage circuit containing an electromagnet which is safe to be turned on and off. on the high voltage circuit we have replaced the switch with 2 metal contacts. one of the contacts connected to a spring to keep the 2 contacts apart. also have an iron block next to the spring.

Question 3

what happens if no current in high voltage appliance?

Answer 3

low voltage turned off so no current flowing through electromagnetic and there is no magnetic field. high voltage turned off as contacts not touching

Question 4

what happens if current flowing in high voltage appliance/how does relay work?

Answer 4

current flows around circuit so now a magnetic field around electromagnet. magnetic field attracts iron block in high voltage circuit causing the contacts to close and switches on the high voltage circuit. if we switch off low voltage circuit there is no electromagnetic field and contacts spring apart + high voltage circuit is switched off

Question 5

Am appliance that uses an ___________ is a ________

Answer 5

electromagnetic, doorbell

Question 6

how does an electromagnetic doorbell work?

Answer 6

• switch closes when buzzer pressed
• causes current to flow through circuit. magnetic field produced by electromagnet
• iron contact now attracted towards the magnetic field. when contact moves towards the magnetic field, the clapper now hits the bell
• at the same time, this breaks the circuit. now no current flowing so no magnetic field. iron contact springs back to its original position. circuit now complete again so a current flows around the circuit and the process is repeated