# Formula booklet physics class 12 chapter Thermo Electricity

## Class- 12 chapter Thermo Electricity

### Formula

• Tn-Tc= Ti-Tn

Tc – Cold junction temperature Tn –Neutral temperature, Ti Inversion temperature

• e = aT + bT2

E – Thermo emf developed T – Temperature difference between junctions a, b – Constants for a given thermo couple

• At neutral temperature, thermo emf is maximum.

• W = i2Rt

W – work done by electricity, I – electric current

R – Resistance of wire t – Time for which current flow.

• Duddell’s thermo galvanometer:

From Q = i2Rt

Qai2

ΔTaQ

icaΔT

θaic

Q = heat produced in heater filament

I = current through heater filament

ΔT = Temperature difference between junctions of thermocouple

Ic = current flowing through thermocouple.

θ = deflection produced in thermo couple.

• Peltier co-efficient

Π = Q/p

Q – amount of heat liberated or absorbed

Q – amount of electric charge flowing.

Unit of Π: J/coulomb or volt.

• Thomson coefficient(σ)

Q – amount of heat liberated or absorbed

i = electric current

t – time for which electric current flows

dT – temperature difference

### CONCEPTUAL POINTS

The heat produced in a given resistor in a given time is proportional to the square of the current in it. i.e. Q ∝ i2.

The heat produced in a resistor by a given current in a given time is proportional to it’s resistance i.e. Q ∝R.

The heat produced in a given resistor by a given current is proportional to the time for which current flows in it. i.e. Q a t

### Seebeck Effect:

If two wires of dissimilar metals are joined to form a closed loop and if the junction are maintained at different temperatures, an emf is developed in the circuit and a current flows through the circuit. This phenomenon is called “Seebeck effect”.

• The emf developed is called thermo emf
• The current produced is called thermo electric current
• The pair of dissimilar metals is called thermo couple.

### Neutral temperature (Tn)

The temperature of hot junction at which thermo emf in the circuit is maximum is called  neutral temperature. It is constant for a given thermo couple.

### Inversion temperature (Ti)

The temperature of hot junction at which thermo emf becomes zero and tends to become negative is called inversion temperature. The difference between neutral temperature.

Academic team of Physics Wallah prepared short notes and all important Physics formulas and bullet points of chapter Thermo Electricity (class-12 Physics).

Download the Pdf of class 12 formula booklet physics of chapter Thermo Electricity from the link given below