Electromagnets Chapter 3.23

What is the primary function of the iron core in a solenoid-based electromagnet?

What occurs to the magnetic field of an electromagnet when the current is turned off?

In a tape recorder, what is the purpose of the erase head?

How does an electric bell continuously ring?

What happens to the magnetic flux pattern around an electromagnet when the current is applied?

Why is careful construction important for the recording head in a tape recorder?

What is a typical frequency used in the erase head of a tape recorder?

What component of the electric bell directly strikes the gong?

What characteristic of soft iron makes it suitable for use in electromagnets?

Which of the following describes the shapes that electromagnets can take?

Electromagnets

A solenoid wrapped around a soft iron core is an electromagnet
The core amplifies the magnetic field produced by the electric current within the solenoid
The magnetic field of the iron bar aligns with the current's field, increasing the overall field strength outside the solenoid
The field quickly fades when the current stops as soft iron loses magnetism easily
Electromagnets can be shaped like bars, horseshoes, or other formats
They produce stronger fields than permanent magnets

Exercise 3.23

If a current passes through a solenoid, an iron core approaching coaxially is attracted into the solenoid
This illustrates magnetic induction

Applications of Electromagnets

Tape Recorders: Use horseshoe electromagnets (tape heads) to magnetize metal-coated tape.
- Small horseshoe electromagnets made of ferromagnetic material are magnetized permanently
Erase Head: The first head on the recorder.
- Used to demagnetize the tape for recording
- High frequency alternating current (about 85 kHz) is used
- Tape is driven at a constant speed through a gap between the magnetic poles of the electromagnets
- Reversing the magnetic field of the electromagnet at the same frequency demagnetizes the tape

Exercise 3.24

a) Magnetic Flux Pattern: Sketch the magnetic flux pattern of the electromagnet inside and near the gap.
b) Overheating Tapes: Avoid overheating the tapes by [this section is incomplete or missing in the document]

The Electric Bell

A continuous bell tone requires a mechanism to switch the current on and off rapidly.
The diagram shows the automatic mechanism in an electric bell.
- Components: Bell Push, Electromagnet, Springy Metal Strip, Contact Screw, Hammer, Gong

Explore the fascinating world of electromagnets in this quiz. Learn how solenoids and soft iron cores work together to create and amplify magnetic fields, and discover their various applications, such as in tape recorders. Test your understanding of magnetic induction through practical examples.