Thermal chemical effect PPT Physics Class 12

 Page 1


THERMAL, CHEMICAL AND THERMOELECTRIC EFFECT
Thermal Effect:
1. Cause of Heating Effect
2. Joule’s Law
3. Electric Power and Electric Energy
4. Electric Fuse
5. Maximum Power Theorem
Chemical Effect:
1. Electrolyte, Electrode & Electrolysis
2. Faraday’s Laws of Electrolysis
3. Faraday and its Relation
4. Application of Electrolysis
5. Primary Cells: Daniel and Leclanche
6. Secondary Cell: Lead – Acid 
Accumulator 
Thermoelectric Effect:
1. Seebeck Effect
2. Seebeck Series
3. Origin of Seebeck Effect
4. Neutral Temperature
5. Temperature of Inversion
6. Thermoelectric Power
7. Laws of Thermoelectricity
Page 2


THERMAL, CHEMICAL AND THERMOELECTRIC EFFECT
Thermal Effect:
1. Cause of Heating Effect
2. Joule’s Law
3. Electric Power and Electric Energy
4. Electric Fuse
5. Maximum Power Theorem
Chemical Effect:
1. Electrolyte, Electrode & Electrolysis
2. Faraday’s Laws of Electrolysis
3. Faraday and its Relation
4. Application of Electrolysis
5. Primary Cells: Daniel and Leclanche
6. Secondary Cell: Lead – Acid 
Accumulator 
Thermoelectric Effect:
1. Seebeck Effect
2. Seebeck Series
3. Origin of Seebeck Effect
4. Neutral Temperature
5. Temperature of Inversion
6. Thermoelectric Power
7. Laws of Thermoelectricity
Joule’s Law:
When an electric current is passed through a conducting wire, the electrical 
energy is converted into heat energy.  This effect is called ‘heating effect of 
electric current’.
It is also called ‘Joule Heating’.
Joule’s Law gives
Q = I
2
R t
Q is in Joule, I in Amp, R in ohm and t in sec.
I
2
R t
J
Q =
Q is in Calorie, I in Amp, R in ohm and t in sec.
Cause of Heating Effect of Current:
When a battery is connected to the ends of a conductor, electric field is set 
up.  The free electrons move in the direction opposite to the field.  They 
undergo collision with the positive ions and atoms of the conductor.  The 
average kinetic energy of vibration of the ions and the atoms increases and 
hence the temperature increases.
Note: The course of electron through resistor is like that of the stone falling 
in water.
THERMAL EFFECT OF CURRENT
Page 3


THERMAL, CHEMICAL AND THERMOELECTRIC EFFECT
Thermal Effect:
1. Cause of Heating Effect
2. Joule’s Law
3. Electric Power and Electric Energy
4. Electric Fuse
5. Maximum Power Theorem
Chemical Effect:
1. Electrolyte, Electrode & Electrolysis
2. Faraday’s Laws of Electrolysis
3. Faraday and its Relation
4. Application of Electrolysis
5. Primary Cells: Daniel and Leclanche
6. Secondary Cell: Lead – Acid 
Accumulator 
Thermoelectric Effect:
1. Seebeck Effect
2. Seebeck Series
3. Origin of Seebeck Effect
4. Neutral Temperature
5. Temperature of Inversion
6. Thermoelectric Power
7. Laws of Thermoelectricity
Joule’s Law:
When an electric current is passed through a conducting wire, the electrical 
energy is converted into heat energy.  This effect is called ‘heating effect of 
electric current’.
It is also called ‘Joule Heating’.
Joule’s Law gives
Q = I
2
R t
Q is in Joule, I in Amp, R in ohm and t in sec.
I
2
R t
J
Q =
Q is in Calorie, I in Amp, R in ohm and t in sec.
Cause of Heating Effect of Current:
When a battery is connected to the ends of a conductor, electric field is set 
up.  The free electrons move in the direction opposite to the field.  They 
undergo collision with the positive ions and atoms of the conductor.  The 
average kinetic energy of vibration of the ions and the atoms increases and 
hence the temperature increases.
Note: The course of electron through resistor is like that of the stone falling 
in water.
THERMAL EFFECT OF CURRENT
Electric Power:
Electric power is the rate at which work is done by an electric current.
P = V I                P = I
2
R             P = V
2
/ R
SI unit of power is ‘watt’.
Other units are ‘kW’ and ‘hp’.
1 kW = 1000 W          1 hp = 746 W
Electric Energy:
Electric energy is the total work done by an electric current in a given time.
E = V I t                E = I
2
R t            E = V
2
t / R
Commercial Unit of Electric Energy is kWh or B.O.T.U.
1 kWh = 3.6 x 10
6
Joule
Electric Fuse:
Electric fuse is a protective device used in series with an electric circuit or an 
electric appliance to save it from damage due to overheating produced by 
strong current in the circuit or appliance.
Fuse is generally made of alloy of 63% tin and 37% lead.  
It has high resistance and low melting point.
Page 4


THERMAL, CHEMICAL AND THERMOELECTRIC EFFECT
Thermal Effect:
1. Cause of Heating Effect
2. Joule’s Law
3. Electric Power and Electric Energy
4. Electric Fuse
5. Maximum Power Theorem
Chemical Effect:
1. Electrolyte, Electrode & Electrolysis
2. Faraday’s Laws of Electrolysis
3. Faraday and its Relation
4. Application of Electrolysis
5. Primary Cells: Daniel and Leclanche
6. Secondary Cell: Lead – Acid 
Accumulator 
Thermoelectric Effect:
1. Seebeck Effect
2. Seebeck Series
3. Origin of Seebeck Effect
4. Neutral Temperature
5. Temperature of Inversion
6. Thermoelectric Power
7. Laws of Thermoelectricity
Joule’s Law:
When an electric current is passed through a conducting wire, the electrical 
energy is converted into heat energy.  This effect is called ‘heating effect of 
electric current’.
It is also called ‘Joule Heating’.
Joule’s Law gives
Q = I
2
R t
Q is in Joule, I in Amp, R in ohm and t in sec.
I
2
R t
J
Q =
Q is in Calorie, I in Amp, R in ohm and t in sec.
Cause of Heating Effect of Current:
When a battery is connected to the ends of a conductor, electric field is set 
up.  The free electrons move in the direction opposite to the field.  They 
undergo collision with the positive ions and atoms of the conductor.  The 
average kinetic energy of vibration of the ions and the atoms increases and 
hence the temperature increases.
Note: The course of electron through resistor is like that of the stone falling 
in water.
THERMAL EFFECT OF CURRENT
Electric Power:
Electric power is the rate at which work is done by an electric current.
P = V I                P = I
2
R             P = V
2
/ R
SI unit of power is ‘watt’.
Other units are ‘kW’ and ‘hp’.
1 kW = 1000 W          1 hp = 746 W
Electric Energy:
Electric energy is the total work done by an electric current in a given time.
E = V I t                E = I
2
R t            E = V
2
t / R
Commercial Unit of Electric Energy is kWh or B.O.T.U.
1 kWh = 3.6 x 10
6
Joule
Electric Fuse:
Electric fuse is a protective device used in series with an electric circuit or an 
electric appliance to save it from damage due to overheating produced by 
strong current in the circuit or appliance.
Fuse is generally made of alloy of 63% tin and 37% lead.  
It has high resistance and low melting point.
Electric Heating Appliances use Nichrome wire (alloy of Ni and Cr).
It is used because:
i) It has high specific resistance   ii) It has high melting point
iii)  It has high malleability               iv) It is not easily oxidised.
For given V,    P a I                P a 1 / R
i.e. i) Higher the power of the appliance, more is the current drawn
ii)  Higher the power of the appliance, less is the resistance.
Maximum Power Theorem:
R
I I
V
r
E
v
R + r
E
I =
Output power of source of emf,        P = I
2
R
R + r
E
P = [
]
2
R
For output power to be maximum, 
dR
dP
= 0
Manipulating, we get        R = r
Maximum Power =
4R
E
2
Page 5


THERMAL, CHEMICAL AND THERMOELECTRIC EFFECT
Thermal Effect:
1. Cause of Heating Effect
2. Joule’s Law
3. Electric Power and Electric Energy
4. Electric Fuse
5. Maximum Power Theorem
Chemical Effect:
1. Electrolyte, Electrode & Electrolysis
2. Faraday’s Laws of Electrolysis
3. Faraday and its Relation
4. Application of Electrolysis
5. Primary Cells: Daniel and Leclanche
6. Secondary Cell: Lead – Acid 
Accumulator 
Thermoelectric Effect:
1. Seebeck Effect
2. Seebeck Series
3. Origin of Seebeck Effect
4. Neutral Temperature
5. Temperature of Inversion
6. Thermoelectric Power
7. Laws of Thermoelectricity
Joule’s Law:
When an electric current is passed through a conducting wire, the electrical 
energy is converted into heat energy.  This effect is called ‘heating effect of 
electric current’.
It is also called ‘Joule Heating’.
Joule’s Law gives
Q = I
2
R t
Q is in Joule, I in Amp, R in ohm and t in sec.
I
2
R t
J
Q =
Q is in Calorie, I in Amp, R in ohm and t in sec.
Cause of Heating Effect of Current:
When a battery is connected to the ends of a conductor, electric field is set 
up.  The free electrons move in the direction opposite to the field.  They 
undergo collision with the positive ions and atoms of the conductor.  The 
average kinetic energy of vibration of the ions and the atoms increases and 
hence the temperature increases.
Note: The course of electron through resistor is like that of the stone falling 
in water.
THERMAL EFFECT OF CURRENT
Electric Power:
Electric power is the rate at which work is done by an electric current.
P = V I                P = I
2
R             P = V
2
/ R
SI unit of power is ‘watt’.
Other units are ‘kW’ and ‘hp’.
1 kW = 1000 W          1 hp = 746 W
Electric Energy:
Electric energy is the total work done by an electric current in a given time.
E = V I t                E = I
2
R t            E = V
2
t / R
Commercial Unit of Electric Energy is kWh or B.O.T.U.
1 kWh = 3.6 x 10
6
Joule
Electric Fuse:
Electric fuse is a protective device used in series with an electric circuit or an 
electric appliance to save it from damage due to overheating produced by 
strong current in the circuit or appliance.
Fuse is generally made of alloy of 63% tin and 37% lead.  
It has high resistance and low melting point.
Electric Heating Appliances use Nichrome wire (alloy of Ni and Cr).
It is used because:
i) It has high specific resistance   ii) It has high melting point
iii)  It has high malleability               iv) It is not easily oxidised.
For given V,    P a I                P a 1 / R
i.e. i) Higher the power of the appliance, more is the current drawn
ii)  Higher the power of the appliance, less is the resistance.
Maximum Power Theorem:
R
I I
V
r
E
v
R + r
E
I =
Output power of source of emf,        P = I
2
R
R + r
E
P = [
]
2
R
For output power to be maximum, 
dR
dP
= 0
Manipulating, we get        R = r
Maximum Power =
4R
E
2
CHEMICAL EFFECT OF CURRENT
Eg. Copper sulphate, acidulated water, 
etc.
Mercury is a good conductor but 
can not dissociate into ions.
Vegetable oil can dissociate into 
ions but can not conduct current.
Electrode: It is a plate or rod through 
which electric current is passed.  The 
electrode though which current enters 
is called anode (+ ve) and the other is 
called cathode (- ve).
Electrolyte: The substances which decompose and show chemical 
reactions when an electric current is passed through them are known as 
electrolyte.
An electrolyte should be capable of i) conducting current and ii) dissociating 
into ions.
E
A
I
Rh
Electrolyte
Electrode