HEATING EFFECT OF ELCTRIC CURRENT

 

                  HEATING EFFECT OF ELCTRIC CURRENT

 

A CELL OR BATTERY IS A SOURCE OF ELECTRICAL ENERGY.  THE CELL OR BATTERY CONSISTS OF A CHEMICAL REACTIONS.

 

THE CHEMICAL REACTION IN CELL OR A BATTERY GENERATES POTENTIAL DIFFERENCE BETWEEN ITS TWO TERMINALS, SO THAT ELECTRON IS IN MOTION. AND ELECTRIC CURRENT IS FLOWING THROUGH A RESISTORS CONNECTED TO THE BATTERY.  A PART OF TEHE SOURCE OF ENERGY IS IN MAINTAINING THE CURRENT MAY BE CONSUMED FOR THE USEFUL WORKS   (LIKE FOR ELECTRIC HEATER , ELECTRIC FAN , ELECTRIC IRON). REST PART OF THE SOURCE ENERGY MAY NE USED TO HEAT TO INCREASE THE TEMPERATURE OF THE EQUIPMENTS OR DEVICES OR GADGETS.

FOR EXAMPLE  :-- THIS HAPPEN IN DAY TO DAT LIFE OR DAILY LIFE. AN ELECTRIC FAN GETS HEAT, WHEN ITS USED FOR LONGER TIME.

IT MEANS TO SAY THAT , IF THE EECTRIC CIRCUIT IS PURELY RESISTIVE, THAT IS THE CONFIGURATION OF THE RESISTORS IS CONNECTED TO A BATTERY. THE SOURCE OF ENERGY CONTINUOSLY GET DISSIPATED ENTIRELY IN THE FORM OF ENERGY OR HEAT. THIS IS CALLED HEATING EFFECT OF ELECTRIC CURRENT.

 

 

THE HEATING EFFECT OF ELECTRIC CURRENT:--

 

WHEN AN ELECTRIC CURRENT IS PASSING THROUGH A RESISTORS OR CONDUCTOR ,  THE CONDUCTOR EMITS HOT AND PRODUCE HEAT. THIS IS CALLED THE HEATING EFFECT OF ELECTRIC CURRENT.

WHEN AN ELCTRIC CURRENT IS PASSING THROUGH A RESISTOR OR CONDUCTOR , IT PRODUCE HEAT DUE TO HINDRANCE CAUSED BY THE RESISTOR OR CONDUCTOR TO THE CONTINUOSLY FLOW OF CURRENT. THE WORK DONE IN OVERCOMING THE HINDRANCE TO THE CURRENT GENERATES HEAT IN THE CONDUCTOR.

 

 

 

 

 

 

 

PRACTICAL APPLICATIONS OF HEATING EFFECT OF ELECTRIC CURRENT

 

The generated heat in a conductor is mandatory because of electric current. This generated heat is unwanted in many cases as it converts electrical energy in to the heat energy. And this unavoidable heat can increase the temperature of the conductor , and it may effects the properties of the equipment or conductor.  However , heating effect of electric current has many useful applications. And this are based on joules heating.

 

ELECTRIC BULB:--

 

IN AN ELECTRIC BULB , THE HEATING EFFECT OF THE ELECTRIC CURRENT  IS USED TO GENERATES THE LIGHTS. THEN FILAMENT OF THE ELECTRIC BULB MUST RETAIN AS MUCH OF THE HEAT GENERATED AS IS POSSIBLE , SO THAT IT GETS TOO HOT AND EMITS OR PRODUCE LIGHT. BUT AT HIGH TEMPERATURE , IT MAY GET MELTED . AND TO AVOID THIS , METAL  MUST BE HIGH MELTING POINT. SO TUNGSTEN HAS HIGH MELTING POINT  (3380 DEGREE CELSIUS ) AND IT IS USED FOR BULB FILAMENTS. THE FILAMENTS SHOULD BE THERMALLY ISOLATED AS MUCH AS POSSIBLE USING INSULATING SUPPORT. THE BULBS ARE FILLED WTH CHEMICALLY INACTIVE NITROGEN AND ARGON GASES TO PROLONGED THE LIFE OF FILAMENTS. MOST OF THE POWER IS CONSUMED BY THE FILAMENTS AS HEAT AND SOME PART OF THE POWER IS USED IN THE FORM OF LIGHT EMITTED.

 

 

 

ELECTRIC FUSE :-

THIS IS ANOTHER APPLICATION OF JOULES HEATING. IT IS MAINLY USED TO PROTECT THE ELCTRIC CIRCUIT AND APPLIANCES BY STOPPING THE HEAVY FLOW OF ELECTRIC CURRENT. THIS FUSE IS CONNECTED IN SERIES WITH THE COMPONENTS OR DEVICES. THIS FUSE IS CONSISTS OF A PIECE OF THE WIRE MADE OF A METAL OR AN ALLOY OF THE APPROPRIATE MELTING POINT LIKE ALUMINIUM  , COPPER ETC.  IN THE ELECTRI CIRCUIT, THE FLOW OF THE CURRENT IS LARGER THAN THE SPECIFIED   VALUE ,  THE TEMPERATRE OF THE FUSED WIRE GETS INCREASED. AND DUE TO THIS INCREASED   TEMPERATURE     , WIRE GET METS AND BREAKS THE CIRCUIT. USUALLY    THE WIRE IS ENCASED IN A CATRIDGE OF PORCELAIN OR SIMILAR MATERIAL WITH METAL ENDS. THE FUSES  IN DOMESTIC PURPOSES ARE RATED AS 1A , 2A, 2A ,5A, 10A ETC..

 

 

JOULE’S LAW OF HEATING:--

 

LET US CONSIDER THAT , THE CURRENT I IS FLOWING THROUGH A RESISTOR ( OR CONDUCTOR) (R) . AND POTENTIAL DIFFERENCE ACROSS THAT RESISTOR IS V. LE THE TIME (t) DURING WHICH A CHARGE (Q) IS FLOWING THROUGH A RESISTOR R.

THE WORK DONE IN MOVING THROUGH THE CHARGE (Q) THROUGH A POTENTIAL DIFFERENCE (V) IS   VQ.

THEREFORE , THE SOURCE ENERGY MUST SUPPLY ENERGY EQUAL TO VQ IN TIME t .

HENCE THE POWER INPUT TO THE CIRCUIT BY THE SOURCE IS:-----

 

P = V  *   Q/t   =  VI

 

ENERGY SUPPLY TO THE CIRCUIT BY THE SOURCE IN TIME  (t) , IS P * t , THAT IS VIt.

THE EXPENDED ENERGY BY THE SOURCE GETS DISSIPATED IN THE RESISTOR IN THE FORM OF HEAT.

THUS FOR A STEADY CURRENT (I) , THE AMOUNT OF HEAT IT PRODUCED IN THE TIME ( t ) IS:--

 

H = VIt

 

APPLY OHM’S LAW ,

H = I^2 Rt

THIS IS CALLED AS JOULE’S LAW OF HEATING.

 

THIS LAW IMPLIES THAT HEAT PRODUCED IN A RESISTOR OR CONDUCTOR IS DIRECTLY PROPORTIONAL TO THE :--

 

(1)  THE SQUARE OF THE CURRENT FOR A GIVEN RESISTOR.

(2)  RESISTANCE  FOR GIVNEN CURRENT

(3)  THE FOR WHICH THE CURRENT FLOWS THROUGH THE RESISTOR.