Physical principal, Properties, and physiological effect of heat.

1. ASSIGNMENT
On
Physical principles of Heat and its properties.
Course: Bsc in Physiotherapy
Subject: Electrotherapy
SUBMITTED TO:
Md. Akhsaful Imam (cPT)
MPT-Ortho, BPT, CMT
Consultant & Head of Physiotherapy, EHC
Assistant Professor, Department of Physiotherapy, CIMT
Reg. No: PH120107 (UK), MBPA-0110 (BD), cPT-71
SUBMITTED BY:
Md. Rokanuzzaman
Bsc in physiotherapy
Roll No: 11
Submission Date: 05.10.2020

2. Physical principle of Heat and it’s properties.
Heat: It is a form of energy that increases the temperature of surrounding tissues or objects.
Heat depends on the mass and energy of the particles. Heat flows from hot to cold until the heat
is balanced which we call equilibrium.
It is measured in calories, joules, or BTUs.
Temperature: Temperature is a relative measure of the speed of the particles.
Temperature is measured in degrees. The 2 main temperature scales are Celsius and Fahrenheit.
Temperature and heat are not the same.
Specific heat: The amount of energy needed to raise the temperature of 1 kg of a substance by 1
degree Celsius.
It is the ability of a substance to absorb heat.
This property can help identify substances.
Example of Specific Heat: How much energy does it take to raisethe temperature of 2 kilograms
of water by 3°C (specific heat of water is4,184 J/kg°C)
Solution: 2 kilograms x 3°C = 6 kg°C
4,184 J/ kg°C x 6 kg°C = 25,104 J
Types of Heat:
A. According to the moisty- (1) Moist Heat (2) Dry Heat
B. According to the Deep of Penetration- (1) Superficial Heat (2) Dry Heat
Difference between Moist Heat and Dry Heat:
Moist Heat Dry Heat
The moist heat has water and system No use of water and system
Sterilization with coagulation of protein Sterilization with oxidation
This process is under pressure This process is on direct flame
Process takes less time Process takes more time
Moist heat is produce by boiling and autoclave Dry heat is produce by Flame and Incineration.
Example: Hot water bath, Wax bath,
Hydrotherapy packs, Contrast bath and steam
bath.
Example: IRR,SWD, MWD, Electric heating
pads etc.

3. Difference between Supperficial Heat and Deep Heat.
Features Superficial Heat Deep Heat
Definition Heats the superficial tissue Heats the deep tissue
Depth of
penetration
3-5 mm Over an inch
Physiological
effects
Reduce pain and muscle spasm Reduce inflammation, pathology of
deep structure
Example Heating pad, IRR, Wax therapy SWD, Ultrasound
Process of transmission: Heat can be transmission by following three ways-
1. Conduction
2. Convection
3. Radiation
Conduction: When heat is transmitted in a component from the area of high temperature to the
area of low temperature but hot particle do not change their place, the process is called
conduction.
Process of conduction: If one end of a solid metal rod is heated, the energy added cause an
increase vibration of the molecules and heat is transmitted to them and in this way, heat is
conducted along the bar from the area of high temperature to areas of lower temperature.
Convection: It takes place in a liquid or gas. If one part of the fluid is heated, the kinetic energy
of molecules in that part is increased, they move further apart and this part becomes less dense.
Consequently, less dense part goes upwards and more dense part comes downwards to take its
place. A change of place of liquid and/or gas occurs and finally, all contents are heated evenly.
Radiation: Heat may be transmitted by infra-red electromagnetic radiation. The heating of
certain atoms causes and electron to move to a higher energy electron shell, The energy is
released as a pulse of infra-red electromagnetic energy.
Latent Heat: A specific amount of heat required to change the state of a particular substance. It
may either from solid to liquid or liquid to gas or vice versa. The heat is called latent heat. In this
situation, the temperature remains same.
Latent Heat of fusion: It is the amount of heat which is required to change the state of a
substance from solid into liquid.
As for Example- in case of water, 1 gram of Ice at 0⁰C requires 336 joules of energy to convert
into 1 gram water at 0⁰C.

4. Latent heat of vaporization: It is the amount of heat which is required to change the state of a
substance from liquid into gas.
As for Example- in case of water, 1 gram water at 100⁰C requires 2268 joules of energy to
convert into 1 gram steam at 100⁰C.
Properties of Heat: Heat is a form of energy and not a physical substance. Heat has no mass.
Heat can move from one place to another in different ways: The measure of how much heat is
needed to cause some change in temperature for a material is the specific heat capacity of the
material.
Physiological effects of heat :
 Increase metabolism
 Increase the extensibility of collagen tissues.
 Decreasing joint stiffness.
 Reducing pain
 Relieving muscle spasm
 Reducing inflammation
 Reducing oedema.
 Reducing aids in the post-acute phase of healing
 Increase blood flow
 Increase nerve stimulation.