PLANCK’ CONSTANT

READ THE WARNING ON THE NEXT SLIDE BEFORE

STARTING THE EXPERIMENT

OPEN AC MAINS CONNECTIONS!

RED ALERT

● THIS EXPERIMENT INVOLVES OPEN AC VOLTAGE CONNECTIONS

● FIRST SWITCH OFF ALL THE AC MAINS CONNECTIONS; THEN MAKE THE CIRCUIT;

● DON’T EVEN ACCIDENTALLY TOUCH THE OPEN CONNECTIONS WHEN SWITCHED ON

APPARATUS USED IN THE PLANCK’S CONSTANT DETERMINATION EXPERIMENT

VARIAC

PHOTODIODE BOX WITH FILTERS

AC AMMETER

Battery eliminator

AC AND DC MILLIAMMETER (ONLY THE DC RANGES ARE USED)

VARIAC PLUG WHICH SHOULD BE REMOVED (SWITCH OFF FIRST) BEFORE MAKING THE CIRCUIT

PHOTODIODE BOX

A TUNGSTUN FILLAMENT BULB CONNECTED TO THE VARIAC

PHOTODIODE

FILTER IN FRONT OF THE OPENING

THE LIGHT FROM

THE BULB

FALLS ON THE

PHOTODIODE

THROUGH

THE FILTER

CHANGING THE FILTERS

WHEN YOU SEE

RED ON THE TOP

THE RED FILTER IS

ACTUALLY

VERTICALLY

BELOW IT AND

INFRONT OF THE

PHOTODIODE

HOW TO OPERATE THE VARIAC

A VARIAC TAKES IN AC MAINS AND GIVES OUT A VARIABLE VOLTAGE AC.

TAKE CARE NOT TO TOUCH THE OPEN WIRES/POINTS FROM THE VARIACSWITCH OFF AC MAINS FIRST; REMOVE THE PLUG; MAKE THE CIRCUIT CONNECTIONS; PLUG IN THE VARIAC AND SWITCH IT ON

THE VARIAC IS CONNECTED TO AC MAINS AND THE OUTPUT IS CONNECTED TO THE BULB AS SHOW LATER ON

TURN THE KNOB TO THE DESIRED OUTPUT VOLTAGE

`

THE NUMBER AGAINST THE POINTER REPRESENTS THE MAXIMIM DEFLECTION CURRENT IN MILLIAMPERES; IF THIS IS 1 mA AS SHOWN THEN IT IS CONVENIENT TO USE THE OUTER SCALE WHICH HAS 100 DIVISIONS.

HOW TO USE THE AMMETER: USE THE LEFT SIDE FOR DC MILLIAMPERES

THIS METER IS USED TO KNOW THE

CURRENT THROUGH THE PHOTODIODE

THE METER IS

SHOWING 60 ON

THE SCALE OF 100

AND THE RANGE

SELECTION KNOB

WAS POINTING AT 1

mA so the current

flowing is 0.6 mA.

FOR THE SAME CURRENT IF WE CHOOSE THE

RANGE AS 3 mA THEN IT IS CONVENIENT TO

READ FROM THE LOWER SCALE ON THE DIAL:

SINCE FULL SCALE DIFLECTION SHOULD BE 3

mA (which corresponds to 30 divisions) 6 DIVISIONS

CORRESPOND TO 0.6 mA

AS BEFORE

TWO CIRCUITS

PALE RED AND THE BLACK ARE THE WIRES FROM THE BULB; THESE ARE CONNECTED TO THE VARIAC VIA (yellow) AMMETER AS SHOWN

CIRCUIT ONE:THE BULB CIRCUITSWITCH OFF THE VARIAC; REMOVE ITS PLUG;

CONNECT ITS OUTPUT TO THE BULB WITH THE AC AMMETER IN SERIES AS SHOWN; THE VOLTAGE IS READ FROM THE VARIAC DIAL; CURRENT FROM THE AMMETER

ONLY WHEN YOU HAVE MADE THIS CIRCUIT PLUG IN THE VARIAC AND SWITCH IT ON; NOW DON’T TOUCH THE OPEN PART OF THIS CIRCUIT; TURN ONLY THE KNOB

BULB CIRCUIT AT A GLANCE; STEP BY STEP GIVEN LATER ON

CIRCUIT TWO: PHOTODIODE CONNECTION

THIS IS A LOW VOLTAGE DC

CONNECTION

THE BATTERY

ELIMINATOR IS

CONNECTED TO THE

PHOTODIODE WITH THE

AMMETER IN SERIES

PHOTODIODE CIRCUIT AT A GLANCE; STEP BY STEP GIVEN LATER ON

PROCEDURE

● AFTER MAKING THE CIRCUIT FOLLOW THE PROCEDURE GIVEN

IN THE MANUAL

● BRIEFLY: FOR A GIVEN FILTER VARY THE VOLTAGE NOTING

DOWN THE CURRENTS THROUGH THE BULB AND THROUGH

THE PHOTODIODE; DO THIS FOR THE THREE FILTERS

STEP BY STEP BULB CIRCUIT

THIS BEING AN AC CIRCUIT THE POLARITIES DON’T

MATTER; NOT MUCH TO WORRY WHETHER YOU TAKE

THE RED OR THE BLACK WIRE LEADING TO THE BULB;

FOR THE SAME REASON YOU WILL GET A SHOCK BY

TOUCHING ANY ONE IF THE CIRCUIT IS ON!

TWO WIRES LEADING TO THE BULB

ONE OF THE WIRES (BLACK ) LEADING TO THE BULB IS CONNECTED TO ONE OF THE OUT PUT

POINTS OF THE VARIAC

IGNORE THE BLACK-WHITE WIRE IN THE BACKGROUND!

ANOTHER WIRE (YELLOW) CONNECTS THE OTHER POINT OF THE VARIAC TO ONE OF THE POINTS (BLACK) OF THE AC AMMETER

THE SECOND WIRE (RED) LEADING TO THE BULB IS CONNECTED TO THE REMAINING POINT (RED) OF THE AC AMMETER

THE PHOTODIODE CIRCUIT

THIS IS A DC CIRCUIT SO POLARITIES DO

MATTER. READ THE MANUAL CAREFULLY

BEFORE MAKING THE CONNECTIONS AS

SHOWN TO BE DOUBLY SURE. IF IN DOUBT

GET THE CIRCUIT CHECKED BEFORE

SWITCHING ON THE BATTERY ELIMINATOR

THE METER IS SHOW VERTICAL FOR CLARITY; YOU SHOULD KEEP IT HORIZONTAL ONLY; OTHERWISE ITS POINTER WILL BE DEFLECTED

UNDER ITS OWN WEIGHT

http://nobelprize.org/nobel_prizes/physics/laureates/1918/planck.html

Max Karl Ernst Ludwig Planck

Born: 23 April 1858, Kiel, Schleswig (now Germany)Died: 4 October 1947, Goettingen, West GermanyAffiliation at the time of the award: Berlin University, Berlin, GermanyPrize motivation: "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta"Field: Quantum mechanicsMax Planck received his Nobel Prize one year later, in 1919.

WHAT IS A PLANCK LENGTH?

THIS QUESTION HAS NOTHING MUCH TO DO WITH

THIS EXPERIMENT AND THERE IS NO FEAR THAT

YOU MAY BE ASKED THIS IN THE VIVA OR THE

COMPRE;

BUT

THERE IS A LIFE BEYOND GRADING!

END