COMPUTER DATA STORAGE

The hard disk of a computer consists of a number of flat, circular plates. Each one of these plates is coated with tiny magnetic particles. The hard disk also contains a controlling mechanism called the read/write head. This is positioned slightly above the magnetic plates. Data is sent to the disk as a series of electrical pulses. These are sent to the read/write head, which contains a tiny electromagnet. The head magnetizes the tiny magnetic particles on the surface of the plates. This pattern of particles on the disk represents the data. You can see how this happens in the project.

When reading information, the magnetized particles on the hard disk create a small current in the head as the plates spin under it. This is then converted by circuits into binary code, a number system that computers use. The code is based on just two numbers (binary means two), 0 and 1. Different combinations represent the letters the letters of the alphabet.

YOU WILL NEED

• Pen or pencil,
• compass,
• white card,
• scissors, ruler,
• red marker pen,
• non-hardening modeling material,
• plastic drinking cup,
• thumb tack,
• paper clips,
• magnet.

STEP 1
Draw a circle with a diameter of 8in on the piece of white card. Draw three more circles inside, each with a diameter 3/4 in smaller than the one before. Cut out the largest circle.

STEP 2
Position a ruler at the center of the circle where the compass point has made a hole. Draw four lines through the middle to divide the circle into eight equal parts.

STEP 3
Use a red marker to color in six or seven sections as shown above. Leave the remaining sections white. The white areas represent full disk space. Red areas are empty disk space.

STEP 4
Attach some modeling material to the rim of a plastic cup. Then turn it upside down on a smooth surface. Press it down gently to make sure it is secure. Place the disk on top.

STEP 5
Push the drawing pin through the middle of the disk into the cup. Make sure the disk can turn. Scatter paper clips on the surface. Hold the magnet under the disk. Move it around.