Electromagnetic Lab Equipment
ElectroMagnetic Steampunk : Or the stuff that has been in the prep room for years and nobody knows what it is.
Many of these objects were once used in A level physics but now in the age of digital multi meters their days have passed and most people do not need to know.
or gravelator as my daughter says, and she wants to be a vet!
It is a coil with a compass. And various connections, and nice little feet for leveling it with.
My one was made by Philip Harris quite some time ago.
When a current is passed through the coil it induces a magnetic field, this makes the compass move. It seems there are two main uses, one is to determine the magnetic field of the earth, alternatively it can be used to calculate the resistance of a telegraph cable.
Very pretty though.
A very sensitive galvo, it has a mirror on a coil and the idea is to shine a light through the collimator onto the mirror and then it bounces off and onto the scale, incredibly heavy for what it is, this one dates from the 1950s but they were used as receivers for transatlantic telegraph cables as they could measure very small currents. And so they were part of the Victorian Internet!
Earth Inductor or Delzennes Circle
This is one of the classics for being on a cupboard of the physics room and collecting the dust
from thousands of kids.
It can measure the magnetic field of the earth, with considerable accuracy, providing it is clean, not like mine which I will get to soon. It has to be accurately aligned with the earths field, including the dip angle, then the coil is swung through 180 degrees and a current is induced, if it is connected to a ballistic galvanometer, sorry I have not got one, then the total charge can be measured and the field strength calculated.
It is basis on many electronic compasses used today, and quite interesting.
Notice the flecks of paint on mine, where the lab was redecorated and nobody bothered to move the kit!
Exploder dynamo MKII
This tired old piece of kit is the thing that they used to use for blowing stuff up. Turn the handle until the light comes on, shout "Firing" and press the button and hey presto the charge goes bang. Sadly this one does not seem to hold a charge and I am not sure I can get it to go.
A variable resistor for use with a mirror galvo I think, wonderful name though.
I think this is for the mirror galvo too, absolutely beautiful old variable resistor.
Westminster High Voltage detector
This thing looks like a lance, the idea seems to be to hold it in your hand and approach a MAINS high voltage source and see if it lights up. Brave!!
Wall of Galvanometers
Funny how suddenly you seem to have got a few of these.
The Wheatstone Bridge
A long wire and a ruler all in one.
The wire has a known resistivity and can be used to find the balance point for unknown currents and can also be a very sensitive variable resistor. Acting as a slide wire potentiometer
Wheatstone Resistance Box
This is a more fancy Wheatstone with keys to alter the resistance,
some times these are described as resistance boxes, which it can be used at too.
Davis and Kidder's Patent Electro-Magnetic Machine
Ariel Davis, 1854
Not strictly something you might find on the bench.
In this case it belonged to my Grandfather and it is still in the condition in which it was passed to me.
A magneto machine that uses a horseshoe magnet to produce a current that you then pass though the patient and it makes them feel better, at least when it stops!
It claimed to cure everything.
My esteemed ancestor apparently use to put a penny in the bottom of a bucket full of water, cranked it furiously and told his children that if they could get it out they could have it. My mum said he was a lovely bloke!
Gold Leaf Electoscope or Electrometer
This glass and wood instrument is for measuring electric charge. A charged object is touched to the top plate and then the small piece of gold leaf attached to the lower end of the metal bar will stand up, the similar charge on both it and the plate repel each other. Touch another charged object to the plate and if it is the same sign the foil will move further out, if it is the opposite charge it will come back down.
The violet Ray
This great bit of quack medicine is a tesla coil used in the early twentieth century for “health” benefits. The idea was to place the strangely shaped glass tubes into the hand held coil and stroke the afflicted body part with the tube. The patient would feel a small electric shop. Judging by the shape of some of the tubes my set came with, I hate to think what body parts they were meant for or where they have been. When I'm feeling brave I'll sort out a video.