1. Example The linear expansivity of a material is 15 X 10 -5 K -1. If the initial area is 25m 2,and then heated through 40 0 C, calculate 1. The increase in area. 2. The cubic expansivity.

2. Real and apparent expansivity of liquid Real and apparent expansivity of liquids are considered because, the expansion of liquid is complicated by the expansion of their containers. The real (or absolute) expansivity of a liquid (ɣ r ) : is the increase in volume per unit volume for one degree rise in temperature. The apparent cubic expansivity of a liquid (ɣ a ) : is the increase in volume per unit volume for one degree rise in temperature when the liquid is heated in an expansible vessel. Mathematically. (ɣ a ) = volume of liquid expelled = mass of expelled liquid volume of liquid remaining X temp rise Mass of liquid remaining X temp rise

3. Expansion of glass A thick glass tumbler cracks when hot water is poured into it because, the inside expand more rapidly than the outside and causes a strain in the glass. A type of glass known as Pyrex is therefore used for making laboratories beakers and flask to avoid the above effects.

4. Anomalous (unusual) expansion of water Water expands when heated and also expand when cooled from 4 0 c and below only. It makes rivers to freeze from the top surface. During winter season, ice forms at the surface of the water while, the bottom of the lake remains at 4 0 c warm enough for the survival of aquatic life. The expansion of water (ice) is also responsible for the cracking of tumbler containing ice.

5. ASSIGNMENT 1.A brass is 2m long at a certain temperature. What is its length for a temperature rise of 100K, if the expansivity of brass is 18 X 10 -5 K -1 2. The linear expansivity of a cube is 12 X 10 -5 K -1. If the length of each side is 10 cm, find the area of one face of the cube and the volume of the cube when its temperature is raised by 30K. 3. A solid metal cube of side 10cm is heated from 10 0 C to 60 0 C. If the linear expansivity of the metal is 1.2 x 10 -5 K - 1 calculate the increase in it’s volume.

6. Heat transfer Since heat is a form of energy, it can be transfered from one place to another and it can be used to do useful work The three modes of heat transfer are; 1.Conduction 2.Convection 3.radiation

7. Heat transfer continues Conduction Metals are good conductors of heat and electricity. Conduction of heat is a process by which heat is passed along a metal object from one particle at higher temperature to another at lower temperature without the heat particle appearing to move. Conductors Metals are good conductors of heat and electricity.The rate at which they conduct heat (thermal conductivity) differ from metal to metal Eg. Copper and silver are very good conductors of heat.

8. Applications of good conductors 1.They are used to manufacture electrical equipments 2. Cooking utensils Poor conductors Poor conductors are materials such as paper, cloth, glass, air, asbestos, water, etc. They conduct heat slowly and are non conductors of electricity Applications of poor conductors 1.Handles of cooking utensils 2.Roofing materials 3.Electrical insulators

9. Applications of convection. 1.House ventilation 2.Land and sea breeze 3.Hot water system 4.Rise of smoke in a chimney

10. convection Convection is the process by which heat is transferred in a fluid (liquid or gas) by the actual movement of heat through their molecules. When air is heated below, the hot air becomes lighter (less dense) and moves upward while the cold air moves down thus setting up convection current. Heat is transferred by this process

11. Land and sea breeze

12. The sun heats up the land during the day than the sea. The heated air above the land rises and the cooler air from the sea takes its place. The circulation of air continues as a result of temperature differences. At night, land becomes cooler than the sea. Convection current is responsible for land and sea breeze and circulation of fresh air in a room.

14. Convection current

18. Radiation Radiation is the process by which heat is transferred from the source through a vacuum to another body. Radiation is a process of heat transfer from the source to another object without a material medium. Convection and conduction needs material medium for their propagation. The heat from the sun reaches the earth surface through radiation.

19. The thermo flask A thermo flask is used in keeping the temperature of its contents constant. The thermo flask consists of a double walled glass vessel. The double walled glass vessel consist of the following; a. A vacuum between the wall to prevent heat lost by conduction and convection. b. Two interior slivered inner surface to prevent heat lost by radiation since sliver is a s poor radiator c. Insulating cork to support at the bottom d. An insulating plastic or cork stopper

20. Assignment 1. With the aid of diagram, illustrate land and sea breeze. 2. Make a label diagram of a thermo flask to show its features.

21. Electric charges The word electricity comes from the Greek 300BC which is called Amber. The earth is made up of several static charges.(electricity) Static electricity is defined as electric charge at rest.

22. Electric charge continues Since the earth is made up of several positive and negative charges, there are interactions between the charges which can be observed. A plastic comb rubbed with a cloth will make some one’s hail stand on end if place near it. In the 17 th century. Benjamin Franklin confirmed that there are two types of charges. Negative and positive. According to him, glass rod rubbed with slik becomes positively charge and plastic rod rubbed with fur becomes negative charge. The law of electrostatic states that like charges repel while unlike charges attract.

23. Producing of charges Charges can be produced by 1. Friction When a glass rod is rubbed with silk cloth, the glass rod acquires a charge by friction. Similarly an ebonite rod is rubbed with fur acquires charge by friction.s 2.Contact 3. Electrostatic induction

24. Charging by contact When a charged object touches a neutral object, electrons are transferred from the charge object to the neutral. Electrons can also be transferred through contact and conduction. You can charge a neutral object by contact with a charged object. Charging by contact happens when electrons move from one object to a neutral object.

25. Charging by electrostatic induction Electrostatic induction is the process of charging a neutral body by placing a charge body near it without any contact between the two. It is the process of charging an object electrically by bringing it near another charged object.

26. The gold leaf electroscope Gold leaf electroscope is an instrument used for the detection and testing of small electric charges. It is also used for testing the magnitude of electric charges. It is made up of the following materials as showed in the diagram below. The leaf is the sensitive part of the instrument. Its position indicates the presence of charge in the leaf

29. Lightning and lightning conductor clouds in the atmosphere are made up of several positive and negative charges. Thunder storm generate heavy sparks as lightning (discharge of electrons) due to electrostatic force of attraction between positive and negative charges in the cloud. During the discharge of electrons to earth, lightening strikes the tallest part of the building. The current passing may produce tremendous heat that can set house ablaze.

32. Action of lightning conductor Lightning conductor is used to protect building from thunder strike. It is made up of a long copper stripe with sharp spikes at the top. It is connected from the top of the building down to the ground beneath the earth surface. During lightning, discharged electrons strikes the sharp spikes of the lightning conductor and the excess current flows through it to the ground safely.

34. Force field

35. A force field is a region where gravitational, magnetic or electric force can be felt. These are forces whose sources do not require contact with the body to which they are applied to. Gravitational field Gravitational field is a region or space around a mass in which gravitational force of the mass can be felt.Eg force of gravity.

36. Magnetic field Magnetic field is a region around a magnet or current carrying conductor where a magnetic force is felt. Magnet generates magnetic lines of forces running from north pole to south pole of the magnet. The region of this lines of forces is called magnetic field Magnetic field lines of forces: these are imaginary lines drawn from the north pole to the south pole of a magnet to indicate the direction of magnetic field around the magnet

38. Properties of magnetic field 1. Like poles repel and unlike pole attract 2. Magnetic field lines of forces runs from north pole to south pole

39. Properties of magnetic field

40. Magnet The ancient Greeks discovered magnet many centuries ago. It was found out that a certain Iron ore called lodestone or magnetite exhibit magnetism. Magnetite has the property of pointing the north and south pole direction of the earth when suspended freely. In the periodic table, transition metal has the property of para- magnetism. They are Iron, cobalt, nickel and ferrous alloy. A magnet is a metallic object that has the power to attract other metallic substance. When a magnet is broken into two, instead of separating the north and south pole, it forms two smaller magnets. Each of the two smaller has half the strength of the original magnet. The two types of magnet are: 1.Permanent magnet 2.Temporary magnet e.g electromagnet