School Science Laboratory Equipment

The Carey Foster bridge is a bridge circuit used to measure medium resistances or to measure small differences between two large resistances. It was invented by Carey Foster as a variant on the Wheatstone Bridge. It is also used for accurately measuring small differences in resistance. It is especially useful for determining the resistance per unit length of a wire and measuring low resistances with high precision.

The core of the apparatus is a torsion pendulum made of a light bar with two small lead spheres, which is suspended horizontally from a thin wire. The apparatus is moved from its rest position by the attraction of the two spheres to two larger lead spheres. When the two large spheres are rotated to a new position, the torsion balance will vibrate about a new rest position. The rotary motion is measured using a capacitive differential sensor, which largely suppresses noise and vibration components in the signal. The output is then recorded using a computer. For subsequent evaluation, the data can be exported to a spreadsheet. Alternatively, the motion can be demonstrated with the aid of a light pointer.

Compound Pendulum (Steel C.P.) is a rigid body that oscillates about a horizontal axis under the influence of gravity. Unlike a simple pendulum, which consists of a mass suspended by a string, a compound pendulum has distributed mass and can be made from materials such as steel for higher rigidity and durability.