### Does water swirl counter-clockwise in the Southern Hemisphere?

Answer:Yes and no. When applied to toilets and sinks, this is one of those “too good to be true” science factoids, I’m afraid. But it does apply in some situations.

The myth goes that if you flush a toilet in Australia the water swirls down the drain the opposite way than in the northern hemisphere, due the Coriolis effect (an apparent force which describes how objects veer to the left or right when traveling on something that’s rotating — see the link above for a good visualization of this).

If there were no other forces on that water in the sink or toilet, that would be true. The Coriolis effect does actually make hurricanes rotate the opposite direction in the two hemispheres. But for toilets and sinks it’s another story. The toilet myth is easy to dispell — just peek around the rim of the toilet and you’ll see that the water is jetted into the bowl at an angle, which determines the direction the water swirls. Sinks, however, are a little more tricky.

I’ve heard of charlatans who hang around the equator in Kenya, carrying basins of water. They’ll stand on the southern side of the equator with the basin, pull a plug at the bottom, and show that it swirls out counter-clockwise. Then they’ll walk to the northern side of the equator, fill the basin and pull the plug, and it swirls out clockwise. Irrefutable proof? Be careful! You have to know all the initial conditions in any experiment, and in this one, there is one that is hidden from you. The huckster just has to add a slight rotation to the water before letting it out (for example, pour the water in at a very slight angle to give it an initial rotation, and it will “remember” that rotation as it swirls out of the basin. In fact, you can swirl the water in the basin, then walk away from it for several hours, and it will still “remember” that rotation when you pull the plug! Plus, the charlatans got it backwards — water should actually swirl counter-clockwise in the northern hemisphere if the Coriolis effect were at play! (See Alistair Fraser’s website for a great explanation of how you can re-create this fakery for a fun party trick!)

Even if you don’t give the water an initial swirl, tiny pits and imperfections in the basin can give the water a rotation — which may be clockwise or counterclockwise, but doesn’t depend on which hemisphere you’re in!

### COMMON COLLECTOR CONFIGURATION OF A TRANSISTOR

COMMON COLLECTOR CONNECTION

In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

Common Collector Transistor Circuit

In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by

COMMON COLLECTOR CIRCUIT

A test  circuit  for determining the  static characteristic  of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits.   To   measure   the   base   and   the   emitter   currents,   milli   ammeters   are connected in series with the base and the emitter circuits. Voltmeters are connected   across the input an…