UNIT 2.4 Electricity PDF

**2.4 [Electric Circuits]** Learning Outcome:- 2\. **How cells and batteries provide electricity?** *i. Explain how cells and batteries provide electricity* *ii. Connect electrical components of a given simple circuit diagram* *iii Draw a circuit diagram of a picture or a real life connected el...

**2.4 [Electric Circuits]** Learning Outcome:- 2\. **How cells and batteries provide electricity?** *i. Explain how cells and batteries provide electricity* *ii. Connect electrical components of a given simple circuit diagram* *iii Draw a circuit diagram of a picture or a real life connected electrical circuits.* -- -- *i. Describe properties of conductors and insulators in terms of flow of electrons.* ***[Conductors]*** Conductors are something that conveys heat of electricity (a substance, body or medium that allows heat, electricity, light or sound to pass along it or through it). In conductors, atoms hold on only loosely to some of their electrons. These electrons move through the material by passing from atom to atom, pushing other loose electrons ahead of themselves*.* - *used in overhead electrical cables* ***[Exercise 2.41]: Conductors and Insulators**.* 1. *Explain the difference between a good conductor or electricity and a good insulator.* 2. *a) List three good conductors.* *b) List three good insulators.* +-----------------------------------------------------------------------+ | 2\. **How cells and batteries provide electricity.** | | | | *i. Explain how cells and batteries provide electricity.* | | | | *ii. Connect electrical components of a given simple circuit | | diagram.* | | | | *iii Draw a circuit diagram of a picture or a real life connected | | electrical circuits.* | +-----------------------------------------------------------------------+ *i. Explain how cells and batteries provide electricity.* ***[Cells and batteries]*** *ii. Connect electrical components of a given simple circuit diagram.* ***[Electrical components]*** +-----------------------+-----------------------+-----------------------+ | **Component** | **Symbol** | **Function** | +=======================+=======================+=======================+ | 1. | | -Supplies electrical | | | | energy | | | | | | | | -The larger terminal | | | | indicates the | | | | positive (+) | | | | | | | | -A single cell is | | | | often interpreted and | | | | called a battery, but | | | | a battery is two or | | | | more cell joined | | | | together. | +-----------------------+-----------------------+-----------------------+ | 2. | | -Supplies electrical | | | | energy | | | | | | | | -A battery is more | | | | than one cell. | | | | | | | | -The larger terminal | | | | is the positive (+) | | | | and the small | | | | terminal is called | | | | the negative (-) | +-----------------------+-----------------------+-----------------------+ | | | -Supplies electrical | | | | energy. | | | | | | | | -DC = Direct Current, | | | | always flowing in one | | | | direction. | +-----------------------+-----------------------+-----------------------+ | | | -Supplies electrical | | | | energy. | | | | | | | | -AC = Alternating | | | | Current, continually | | | | changing direction of | | | | its currents. It is | | | | negative and then | | | | positive which | | | | alternates again. | +-----------------------+-----------------------+-----------------------+ | | | -A safety device, | | | | which will 'blow' or | | | | melt if the current | | | | flowing through it | | | | exceeds specified | | | | value. | | | | | | | | -Used as a protection | | | | for electrical | | | | circuits. | +-----------------------+-----------------------+-----------------------+ | 6\. Lamp | or | -A component that | | | | converts electrical | | | | energy to light | | | | energy. | +-----------------------+-----------------------+-----------------------+ | | | -A switch controls | | | | the flow of current. | | | | | | | | -It allows current to | | | | flow only in the | | | | closed position. | +-----------------------+-----------------------+-----------------------+ | | or | -A resistor restricts | | | | the flow of current | | | | | | | | -For example: to | | | | limit the current | | | | passing through an | | | | LED | +-----------------------+-----------------------+-----------------------+ | |  | that flows through a | | | Or | component. | +-----------------------+-----------------------+-----------------------+ | | | -The device that | | | | allows current to | | | | flow in only one | | | | direction. | +-----------------------+-----------------------+-----------------------+ | 11\. Light Emitting | | -A component that has | | Diode | | the ability to | | | | convert electrical | | | | energy into light | | | | energy. | +-----------------------+-----------------------+-----------------------+ | 12. Voltmeter | | -A voltmeter is used | | | | to measure voltage. | | | | | | | | -The proper name for | | | | voltage is "potential | | | | difference", but most | | | | people prefer to say | | | | voltage! | +-----------------------+-----------------------+-----------------------+ | 13. Ammeter | | -An instrument that | | | | is used to measure | | | | the current flowing | | | | through a circuit. | | | | Current is measured | | | | in amps. | +-----------------------+-----------------------+-----------------------+ | 14. Galvanometer | | -An galvanometer is a | | | | very sensitive meter | | | | which is used to | | | | measure very small | | | | currents, usually 1mA | | | | or less. | +-----------------------+-----------------------+-----------------------+ | 15. Capacitor | | -Stores electrical | | | | energy | +-----------------------+-----------------------+-----------------------+ *iii Draw a circuit diagram of a picture or a real life connected electrical circuits.* ***Circuit:** circular path (a route or path that follows a curved course and finishes at the point at which it began)* ***[Drawing circuits]:*** Some helpful rules for drawing circuits -*Use a ruler to draw the connecting wires in straight lines* *-Draw components correctly* *-Don't leave gaps in a circuit diagram unless the circuit is meant to be incomplete.*  *-Draw dots to show two wires joined together* ***[Example of circuit diagram]:*** 1. This diagram shows a circuit diagram involving a power pack, a light bulb and a switch in one loop. Note:  2. This diagram shows a circuit involving a power pack, two light bulbs and a switch. ***[Exercise 2.42]: Drawing Simple circuit diagram*** Complete this Circuit diagram drawing. ***a)*** -------------------------- -- b) c) d) -- -- **[TYPES OF ELECTRICAL CIRCUITS]** 1. **SERIES CIRCUITS** 2. **PARALLEL CIRCUITS** 1. -In a series circuit, the electrons all move along the same path, through one component, then another and so on. *For Example:* -The circuit shows a series circuit because the components (lamps) are connected in the same path. \- If one lamp is removed, the other lamp goes out because the current cannot flow in the broken circuit. 2. -In parallel circuits, the current has a 'choice' of pathways. -Most electrons go along the path which is easiest to move through. It is the path with the smallest resistance. -The above circuit shows a parallel circuit because the components are connected in different pathways. -The current has a choice of which pathway it will travel. -If one lamp is removed the other lamp continues to glow because the current can still flow around a complete circuit. **Exercise 2.43:** 1. Give two example of 'electrical components' 2. Alongside is *badly* drawn circuit of a cell supplying electricity to a light bulb. Find the three mistakes in the drawing. 20.jpg 3. Draw a circuit diagram with a cell, two bulbs and a switch in one loop. The circuit should allow both light bulbs to be returned on/off by switch. 4. State which, if any, of the lamps in each circuit below will be on. All of the switches have been left open.  5. Draw a circuit with a power supply, two bulbs and two switches, in which each bulb can be turned on/off by its 'own' switch. **Exercise 2.44:** 1. Draw a circuit diagram for each of the following circuits. 2. Complete the table below by filling them in. **Electrical component** **Symbol** **Function** -------------------------- ------------ -------------------------------------------------- Switch Controls the flow of current Allows the current to flow in only one direction Rheostat 3. Study the circuit diagram below carefully then answer the questions that follow. a. Allow only the lamp to glow b. Allow only the bell to ring c. Allow both the lamp to glow and the bell to ring. 4. Draw a circuit diagram to show a lamp in series with two cells, a switch and a rheostat. 5. Here are some circuit symbols. **I** **II** **III** ---- ---------- ---------- ---------- A. Rheostat Diode Switch B. Lamp Resistor Rheostat C. Lamp Rheostat Switch D. Resistor Resistor rheostat 6. In the electric circuit shown M~1~ and M~2~ are meters. What does the meter labelled M~2~ measure? A. Current B. Voltage C. Resistance D. Power -- -- -- --