Question

The most commonly used gadget that you should know of is a ding-dong doorbell using an electromagnet. In order to make a door bell, please answer the following questions:

1. List the items needed to make a door bell using common household stuff.
2. Draw its labeled schematics, and explain its working principle
3. Which Maxwell’s equation will you use to design the doorbell actuation
4. Describe two ways to make the bell sound loud.
5. List five commercial uses of electromagnets other than doorbell.

Answer 1

1. To design the door bell, following items need:

1. Electromagnet ( Buzzer)

2. Switch

3. Battery ( 5V - 9V)

4. Wires

5. Timer Circuit -: to design timer circuit, the below items need:

A. NE555 IC - 2

B. Resitors (10k, 100k, 1k)

C. Capacitor (1000uf, 1uf)

D. Zero PCB and solder wire and iron

2.

Basic principle behind this circuit is that NE555 IC is used to generate the pulses of different time period. So, we can select the time period by adjusting the value of resistance(R) and capacitor(C).

Time constant, T = R* C

A pulse of desired frequency generated which cause change in electromagnetism and vibrates the film at the buzzer which causes sound.

3. Here change in electrical signal causes creation of magnetic field.

So, Ampere Circuital Law or 4th Maxwell Equation:

4. To make bell sound loud:

A) the voltage of battery can be increased by adding more cell in series with battery. High amplitude of sound is directly proportional to the Voltage given at buzzer.

B) Also, Value of resistance can be adjust so that max power can be transmitted to the buzzer or speaker.

5. Electromagnets are used in:

A) earphones and headphones.

B) Loudspeaker

C) In Cranes, to pick iron garbage

D) Hard disk - to store data

E) Fan - to rotate it