15075 Experiment Pack - Basic Electricity 2 info

STE 15075 Experiment Pack - Basic Electricity 2

INTRODUCTION

This Experiment Pack covers a wide range of essential topics thought 21 graded experiments, and comes with a comprehensive 25 page Instructions and Teaching Guide. It is complementary to the STE 15072 Experiment Pack. Together they form a complete course in elementary electrical phenomena. Each Experiment Pack  can however provide on its own an importnt teaching resource.

TOPICS COVERED

1)           WHAT IS ELECTRICITY?

2)             STATIC ELECTRICITY

3)             PROTONS AND ELECTRONS

4)             ELECTRIC FORCES

5)             ELECTRIC INDUCTION

6)             CONDUCTORS AND INSULATORS

7)             THE ELECTROSCOPE

8)             HOW TO USE THE ELECTROSCOPE

9)             THUNDER AND LIGHTNING

10)         ELECTRICITY IN MOTION

11)         BATTERIES

12)         ELECTRIC CIRCUITS

13)         LIGHT BULBS CONNECTED IN SERIES AND IN PARALLEL

14)         CONVERTING ELECTRICAL POWER INTO HEAT

15)         ELECTRICAL CONDUCTION IN LIQUIDS

16)         ELECTROLYSIS

17)         MAGNETS

18)         MAGNETIC POLES

19)         MAGNETIC EFFECTS OF ELECTRIC CURRENTS

20)         THE ELECTROMAGNET

21)         THE ELECTRIC BELL

EQUIPMENT

EXAMPLE EXPERIMENT

16)         ELECTRICAL CONDUCTION IN LIQUIDS

All electrical appliances contain metal conductors, the most commonly used metal being copper. However, as the following experiment demonstrates, also some liquids can conduct electricity.

EXPERIMENT  15

Equipment needed:          1 beaker, 100 ml; 1 bipolar module; 2 leads, 60 cm long; 2 leads, 30 cm long; 1 bulb with bulb holder; 1 switch; 1 battery holder; 4 torch batteries, 1,5 V (not included); cooking salt (not included).

Pour 40-50 ml of distilled water into the beaker and assemble the circuit as shown in Fig. 1. Close the circuit. The bulb does not light up: distilled water is actually not a good current conductor.

Take some cooking salt (sodium chloride) and a spoon.

Open the circuit, put a small amount of salt into the water and stir the solution using the spoon until the salt has completely dissolved. Now close the circuit: the bulb produces a weak light.

Repeat it several times. Note that the higher the salt concentration in water, the brighter the light.

The same result can be achieved by using an acid or a hydrate instead of cooking salt.

In conclusion, pure water is not a current conductor, whereas solutions of salts, acids or hydrates and water are good conductors. These are called electrolytic solutions.

The chemical structure of the substances used can explain this phenomenon.

A molecule of sodium chloride is expressed by the following formula: NaCl

It is formed by the joining of one sodium atom (Na) and one chloride atom (Cl). The atoms are kept together by electric force, since the sodium atom carries a positive charge (Na⁺) while the chloride atom carries a negative charge (Cl^-). When the salt is dissolved into water, the atoms separate. The sodium atom, being positive, moves towards the negative pole of the battery, while the chloride atom, being negative, moves towards the positive pole.