The
Kelvin Gallery, Hunterian Museum, Glasgow
These
exhibits are in Discovery Disk format, but fastened down
Compass
correction
Magnetic compasses must be carefully adjusted to function in steel
ships.
On the standard base disc is a turntable shaped like a broad, stylised
ship. The front half is red and the rear half blue, with the boundary
skewed at an angle. A small magnet is concealed below the front end, off-centre,
with its south pole facing the centre.
A simple magnetic compass is mounted in the centre of the ship.
Four rotatable plastic knobs, each approximately 25mm diameter, are symmetrically
positioned around the compass. One pair fore-and-aft and one pair athwartships.
Each knob is coloured red and blue and contains a small magnet. A red
plastic cylinder is attached to the bench up to 150mm to the (magnetic)
north of the centre of the base disc. This contains a stronger magnet,
aligned with the earth's magnetic field (not necessarily with the possibly
distorted field surrounding the exhibit).
The challenge is to adjust the four rotatable magnets such that the compass
points north whichever direction the ship is facing.
Hand-cranked
generator
Hand-cranked generator exhibits are better than the 'exercise-bicycle'
versions often seen.
While cranking the handle, four separate push-to-make buttons can be
pressed with the fingers of the other hand. These switch on four lamps
of different wattages, including a high-efficiency LED. The increase in
"load" felt on the crank-handle is very impressive. It is easy
to light the smaller lamps, but extremely difficult to light all three
lamps together.
An ammeter shows current and all the circuitry is clearly visible, for
conceptual clarity.
Heat
pump
Depending which direction you crank the handle, one part of the hand-panel
becomes warmer while the other becomes cooler.
Conductors?
A buzzer and an ammeter indicate which of the six mounted specimens
conduct an electric current and which do not.
Transatlantic
cable
Early submarine cables suffered major problems with electrical resistance
and capacitance.
Green outlines
of Newfoundland and Britain are fixed to the disc, with a red line indicating
the first transatlantic cable. Eleven brass studs connect with the 'cable'.
There is a
push-button representing a Morse key in Newfoundland and a sensitive meter
below the base disc, in front of the 'cable'. A red Superflex insulated
wire with bare metal ferrule at the loose end is attached to the base
close to the meter. Resistors and electrolytic capacitors are arranged
out of sight below the base, such that there is a 4 - 5 seconds delay
at the distant end of the 'cable', and an obvious drop in the meter reading
as distance increases.
Coupled
pendulum
Make sure everything is still, then swing just one of the pendulums.
Now step back, wait and watch what happens. First one pendulum stops
swinging, then the other.
Energy goes from one pendulum to the other.
Friction
wheel
Users spin the wheel fast, then stop it by holding a fingertip against
its rubber rim, feeling the heat generated.
Cartesian
diver
 
Squeeze the bottle and watch what happens.
Notice the sides of the little plastic tube being squeezed smaller before
it sinks.
Does it make any difference if you squeeze the bottom of the bottle instead
of the top?
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