Current Sensor

 Experiment Guide

   

Current Sensor

Introduction:

Part of the Eisco series of hand held sensors, the current sensor allows students to record and graph data in experiments on the go.

This sensor can be used to measure the current in parallel or series branches of low voltage AC and DC circuits and also to investigate the dependence of the current flow through components on the voltage across them. With its 4 mm plugs it can easily be connected into electric circuits.

Sensor Specs:

Range -2.5 – 2.5 A | 0.01 A resolution | 3000 max sample rate

Activity – Converting Energy to Electricity

General Background:

The Eisco Energy Conversion Kit demonstrates several ways in which different types of energy can be converted to electrical energy. The three different processes depicted in the kit are: electro-chemical (C cell batteries), photovoltaic (solar cells), and mechanical (handcrank / DC generator).

The DC generator has been around since the time of Michael Faraday who discovered the operating principle behind electromagnetic generators. Faraday’s law explains how an electromotive force is generated in an electrical conductor that encircles a time varying magnetic field. In the Energy Conversion Kit, a hand crank turns a magnet inside a coil of wire. The changing magnet field produced by the motion of the magnet induces a current in the wire, which can be measured by the Current Sensor.

The generation of electricity from a solar cell is based upon the photovoltaic effect, the creation of electrical current upon exposure to light. The incident sunlight is absorbed by the electrons in the valence band of the atoms in the metal, and jumps to the conduction band and become free. The free electrons are pushed out of the metal, and produce a current that you will measure using the Current Sensor.

The electrochemical cell is a device that creates electrical energy from chemical reactions. The cell is made up of two half-cells which each consist of an electrode (a conductor of electricity) and an electrolyte (a substance that allows migrations of ions between the electrodes). Electrons flows from the negatively charged electrode, called the anode, to the positively charged electrode, called the cathode.

Required Materials:

EISCO Current Sensor & Handheld Unit EISCO Energy Conversion Kit [PH1321] 2 ‘C’ cell batteries

Procedure

1. Plug the red and black leads from the Eisco Current Sensor into the correspondingly colored terminals in the Energy Conversion Kit apparatus.

2. Insert two C-cell batteries into the Energy Conversion apparatus as instructed by the diagram on the cell holder.

3. Turn the rotary dial on the Energy Conversion apparatus to ‘Battery.’ 4. Record the current in the table. 5. Turn the rotary dial on the Energy Conversion apparatus to ‘DC Generator.’ 6. Turn the hand crank that is attached to the DC generator via a drive belt. Vary

the speed at which you turn the hand crank and notice the variation in the current on the sensor. Turn the hand crank as fast as you are able. Record the maximum current measured by the sensor in the table.

7. Turn the rotary dial on the Energy Conversion apparatus to ‘Solar Cell.’ 8. Record the current produced by the solar cell. If possible, take the Energy

Conversion apparatus outdoors to make the measurement. Else, point it out a window to achieve the maximum amount of incident sun light on the solar cell. This obviously has best results on a sunny day.

Data

Power Source Current (A)

Batteries

DC Generator (Hand Crank)

Solar Cell

Questions

1. What generated the most current? What generated the least? 2. Where does the energy come from for each source? What are some reasons

why one might not want to rely on the source that created the most current.

Sample Results

These are examples of possible results. Due to the many variables involved, exact reproduction is unlikely, but students should find similar trends.

Power Source Current (A)

Batteries 2.5 A

DC Generator (Hand Crank)

0.3 A

Solar Cell 0.07 A

Answers to Questions

1. The batteries generated the most current. The solar cell generated the least.

2. The current from the batteries are from a chemical process, current from the DC generator is mechanical energy, and the solar cells current came from the sun. The chemical process involved in the batteries is not a renewable source of energy. The chemical process uses up the potency of the materials. The hand crank as a source of energy is renewable, but one’s arm will most certainly tire at some point. The Sun as a source of energy is fairly infinite. It does depend on the amount of sunlight reaching the cells. And will only work for the lifetime of the Sun.