Category: 15 Electromagnetism

14.A Magnets

There is something magical about magnetism isn’t it? That mysterious repulsion between two magnets. Flip one around and they attract instead. Flip the other one too and they repel again.

Magnets make very fascinating toys. Here are a few.

Using two magnets aligned perpendicular to each other, spinning motion is produced!

Detail at https://xmdemo.wordpress.com/094

Detail at https://xmdemo.wordpress.com/094

This one is epic. A top levitating in the magnetic field of a ring magnet!

Detail at https://xmdemo.wordpress.com/093

14.3.1 Charge Moving in a Magnetic Field

Before the advent of LCD monitors, we had the cathode-ray-tube monitors. CRT monitors are bulky and heavy and there is an electron gun inside spraying electrons towards the RGB coated screen. Perfect for demonstrations of Bqv.

A neodymium magnet causes an explosion of colours on the screen!

Detail at https://xmdemo.wordpress.com/008

Time to bring out Fleming’s Left Hand!

Detail at https://xmdemo.wordpress.com/009

See how a magnetic field works.

Detail at https://xmdemo.wordpress.com/010

See how a magnetic pump.

Detail at https://xmdemo.wordpress.com/900

14.2.1 Electric Motor

A magnetic field can exert a magnetic force on a wire if the wire is carrying a current. (F=BIL). This is the basis for all electric motors.

Here is a home-made toy DC motor: It works despite having no commutator. How come?

Detail at https://xmdemo.wordpress.com/024

2 segments of the wire must be experiencing magnetic forces in opposite directions, in order for the heart to spin. Can you identify the segments?

Detail at https://xmdemo.wordpress.com/035

This motor is rotated by one single torque (instead of a couple). Can you figure out how it works?

Detail at https://xmdemo.wordpress.com/099