Physics

Faraday’s Law and a Basic Seismometer

Objective

Designing seismometers which can differentiate between horizontal and vertical vibrations.

Introduction

We’ll start off our study with Faraday’s law and a look at amplifiers, as learned from the construction of the AM radio receivers. When we’re done with the basic theory of these two fields, we continue to the construction of an appropriate coil and amplifier; giving us our basic seismometer.

Then, after playing with the basic seismometer, we carry on to the design of two apparatuses which must limit the detection of horizontal vibrations and vertical vibrations respectively. Subsequently, we’ll then do experiments, such as determining what vibrations are mainly generated by the train passing by UP daily.

Instructor’s Notes

The students will be introduced to Faraday’s Law, its applications and how an amplifier works.

Each student will be handed a pre-designed amplifier on a PC board with the components (lose) required to construct it. They will then build it on one of the UP with Science days allocated to them, on that same day they will have to also think of an appropriate coil (number of windings and width). The coils (only one type will be chosen) will then be made by the instructor with the help of the departments’ technicians (Gerhard & Jaco).

The students must then come up with a way of restricting the movement of the magnets over the coils, such that only horizontal and vertical vibrations can be picked up. If they fail to come up with adequate ideas, the instructor will help them by for example giving them key words which they can use on the internet or library. The aim in the end is to build the two types of Lehman Seismometers (damping will also be introduced).

There can then be experimented with the two Lehman Seismometers to see whether they pickup horizontal and vertical vibrations respectively.

Experimental Procedure

Components:

Magnet Copper Coil Two LM741 Operational Amplifiers Two LED’s 10MW Resistor 10kW Resistor 470W Resistor Piezo Buzzer Two 9V Batteries

Construction:

Participants

• Mr Louwrens van Schalkwyk
• Dr Walter Meyer