Teacher's Notes

Compiled by Peter Ellis

Here are the answers to the Scientist of the Month Web Activity

1

 By rubbing with a cloth - silk, wool or fur are the traditional materials used.

2

 Current electricity flows through a metal conductor. Static electricity is a charge fixed in one place. Static electricity can be positive or negative (like charges repel, unlike charges attract). When a current flows through a metal wire only one type of charge moves (the negatively charged electrons)

3

For Galvani. Only living matter responded by moving in the way that frog's legs did. The twitching occurred when a static charge (or lightning) was conducted to the frogs'\ legs as well as when they were hung on a hook.

For Volta. Unless they were connected to a source of electric charge the frogs' legs only twitched if two different metals were connected at the same time (in Galvani's original experiment a brass hook was used to hang the frog's legs on iron railings). Two similar metals or other materials had no effect.

4

 Zinc and silver have the biggest difference in reactivity (not counting gold which was too expensive for Volta to use)

5

 Magnesium was not isolated until the early 1800s when Davy used electricity supplied by a large battery to decompose magnesium compounds.

6

 Total voltage = 1.5 x 30 = 45 volts In practice the internal resistance of the pile is high so the actual voltage will be much less than this.

7

required: pieces of zinc and copper foil, beaker, water, salt, wires, bulb, milli-ammeter, voltmeter (0-2 volts)
The bulb can be made brighter and the voltage increased by connecting two or more of the cells in series. The current can be increased by increasing the size of the electrodes, holding them closer together, or by making the solution more concentrated.

8 Papers sent to journals to be peer-reviewed prior to publication on paper or on the internet.
9 If France hadn't invaded Lombardy, Volta may have announced his discovery by publishing in Italian journals in 1799.
10 Even in 1800 science was international. Letters and journals were exchanged even between countries at war and scientists were acclaimed regardless of their nationality. On the other hand politicians were always quick to claim a discovery or invention for their own use, hence Napoleon's adoption of Volta and his reward.
11

-personal stereos, torches, etc. alkaline "dry" cells
-zinc and managanese dioxide (in potassium hydroxide)
-vehicles
-storage batteries
-lead/lead oxide computers,
-mobile phones
-NiCad batteries
-nickel/cadmium (now being replaced by lithium batteries)

 

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The websites were last checked on 8th August 2000