## Thorium as an alternative source of nuclear energy

It's about time Singapore considered building a liquid fluoride thorium reactor as a safe source of nuclear energy. From the video, it would appear that thorium is safe as it cannot be weaponized, does not require high pressure containers and the risk of a meltdown does not exist. For a small island state like Singapore, this presents an attractive way of obtaining relatively clean abundant energy. I'm sure if we think hard enough we will be able to solve the other problems such as storage of waste products.

Perhaps the part of our syllabus on Nuclear Physics will need to be updated then.

## Siphoning water

This video is taken during my IP4 class today. My students are making use of rubber tubes to demonstrate how we can use gravity to siphon water from one place to another. As long as the level of the source is higher than the level of the receiving end, we can do so.

## Homopolar Motor 1

A homopolar motor is a simple electric motor that does not require the use of a commutator. The electric current flows in a fixed direction within the wires of the motor. The following are instructions on how to construct this simple teaching tool that can be used to demonstrate how a motor works, as well as teach concepts such as Fleming's left-hand rule and $\mathbf{F}= I\mathbf{l \times B}$.

Materials

1. Copper wire (about 22 cm)
2. Small neodymium magnets (1 or 2)
3. 1.5 V AA-size battery
4. Base with either another magnet or a iron surface, such as the head of an iron nail

Procedure

1. Make a V-shaped bend in the middle of the copper wire, with about 0.5 cm on both sides of the V-shape. Bend the copper wire into a rectangular loop using the dimensions shown below.
2. Tip: You may use the edge of a wooden block as a guide to bend the copper wires at right angles. A pair of wooden blocks can also be used to flatten the rectangular loop if you press them together tightly with the loop in between.
3. Mount the neodymium magnet(s) onto the magnet or iron base.
4. Hook the wires at the base around the magnets.
5. Place the AA-sized battery with the protruding end on the magnet(s).
6. Complete the electric circuit by placing the V-shaped end of the rectangular loop onto the flat end of the battery and watch the loop spin.
7. Be careful not to keep the current flowing for too long as the battery and wire can get very hot.

Science Explained

1. A force acts on a current if it is placed in a magnetic field. This force is what causes the motor to spin about its axis.
2. To apply Fleming's left hand rule, observe from the diagram below how the magnetic field bends around the magnet and its direction with respect to the direction of current flow. How do you think the loop will spin?

If you are having difficulty making this version of the homopolar motor, try the other design for the homopolar motor made using a screw.