PHYSICS ASSIGNMENT.pptx
- 2. ACKNOWLEDGEMENT I am grateful to my Physics teacher Mrs. for her guidance and constant supervision as well as cooperation in providing all the necessary information regarding the portfolio.
- 3. Introduction What is the Heating Effect of Electric Current? Effects of Heat on the Conductor Heating Effect of Electric Current Formula Joules Law of Heating Factors on which Heat Depends Applications of Heating Effect of Electric Current INDEX
- 4. Introduction When an electric current is allowed to flow through a high resistance wire, such as nichrome wire, the conductor heats up and produces heat. Such a heating action of a conductor is known as the Heating effect of Current.
- 5. What is the Heating Effect of Electric Current? When we use some electrical appliances, the chemical reactions which occur in the cells on which they run generate some potential difference between its terminals which sets the electrons in motion. To maintain the flow of current the source needs to expand some energy. A part of the energy is used in doing some sort of useful work like moving the fan blades in case of electricity- generated fans, etc. The remaining energy is exploited or expanded in the form of heat which raises the temperature of the appliance. If we are using a circuit in an appliance that is purely resistive then a lot of energy is dissipated entirely in the form of what we call heat. This is called or known as the heating effect of electric current.
- 6. Effects of Heat on the Conductor • The heating effect may cause an increase in the temperature of the wire of the conductor. • This may also cause an increase in the volume of the material. • More simply, when an electrical current is passed through a conductor, it generates excess heat due to the resistance caused by the electrons in the conductor to the flowing current. The work done in overcoming this resistance to the current generates what we call heat in that conductor. The electrical heating effect of the electrical current is most commonly and widely applied and used in our daily life. For example, electrical irons, kettles, toasters, electrical heaters, etc. are used widely as alternatives to conventional methods of cooking and also laundry. This same effect is used widely in electrical bulbs which are alternatives to conventional incandescent lamps. These devices have modernized and revolutionized the new sustainable world over the years.
- 7. Heating Effect of Electric Current Formula • Let us assume a current I that is flowing through a resistor that has a resistance of R as shown in the circuit. Let the potential difference across ends of the terminals of the battery be V. Let us assume to be the time during which a charge of Q amount flows across the circuit. The work which is done in moving that charge Q through a potential difference V is V × I. • Hence, the source has to supply energy equal to V × I in time t. Therefore, the power input to the electrical circuit by the source is • P = V × Q/t • = V × I • Or the energy that is being supplied to the circuit by the source in time t is P × t, that is, V × I × t. This extra energy generated gets dissipated in the resistor in the form of heat. Therefore, for a steady and fixed current I, the amount of heat denoted by H that is produced in time t then:H = V × I × t
- 8. Joules Law of Heating The very famous physicist James Prescott found that the amount of heat generated per second that develops in a conductor having a current is directly proportional to the electrical resistance of the wire and also with the square of the current given. This heat which is liberated or generated because of the electrical current that flows in an electrical wire is expressed in Joules. By applying the ohms law to the equation H = V × I × t. We can deduce the Joules law or joules first law which gives the relationship between the heat that is produced by flowing charges of electric current through a conductor. It is directly proportional to the square of the supplied current, the electrical resistance exerted by the appliance, and the time for which we used it. This is known or called joule’s law of heating. The following is its expression: H = I2 × R × t
- 9. Factors on which Heat Depends • The amount of liberated or generated heat is directly proportional to the given wire’s electrical resistance when the electrical current in the given circuit and the flow of supplied current is not altered or changed. • The amount of liberated or generated heat in the conductor carrying current is directly proportional to the square of the electrical current that flows through the given circuit when the electrical resistance and current supply is kept constant. • The amount of heat generated or produced because of the electrical current flow is directly proportional to the time of usage of flow when the electrical resistance and the current flow is constant.
- 10. Applications of Heating Effect of Electric Current • Electric Iron • Electric Heater • Electric Fuse • Electric Bulb