Yr. 9 Electricity WorkBook

Transcription

1 Yr. 9 Electricity WorkBook On completion of this booklet students should be able to: Recall the structure of a neutral atom: three particles, their charges, their location; Nucleus (Proton positive, Neutron- no charge), electron- negative. Recall that there are two types of charges (positive and negative) and how they interact (opposites attract and like charges repel). Recall that static electricity is generated by rubbing two insulators together. Define conductor as a material that allows electrons to travel through it Define an insulator as a material that does not allow electrons to travel through it State that current is a movement of charged particles. Identify names and symbols of basic circuit parts. (wire, bulb, cell, battery of cells, switch, diode, light emitting diode, resistor, ammeter, voltmeter, fuse) Draw circuit diagrams of series and parallel circuits. Understand electrical safety. Fuses- function and wiring. Physical damage to components and wiring. The importance of using an Isolating Transformer or Residual Current Device to protect user from electrocution risk, Circuit overloading fire risk.

2 Static Electricity- charges that are stationary (then move as sparks) 1. Fill in the gaps naming the components of all neutral atoms. Position Name Charge n P N P N C E N 2. How many protons does the atom shown have in its nucleus? 3. How many electrons does the atom shown have? 4. What is the difference between the two numbers? 5. This is called a n atom because it has n c. 6. If the atom above loses one electron. How many positive charges does it now have? How many negative charges does it now have? What is the difference between the two numbers? positive charge. The atom is now p c and wants to attract electrons toward it. 7. The electron that was lost was rubbed off and would have made the other substance n c. This is the basis for Static Electricity. 8. Fill in the gaps. Two substances are rubbed together. One loses e and becomes p c, the other gains the e and becomes n c. 9. If enough charge is rubbed off the e will jump back to another object as a s. We see this from clouds as l.

3 Generating Static Electricity 1. Look at the diagrams and write underneath each one if the effect noticed is a result of static electricity. (Yes / No ) Stream of water attracted to a charged ruler Hair attracted to a brush. Crackle as you take off a jersey. Lightning discharge Nails sticking to a magnet. Paper being lifted by a plastic pen. A jolt from a trampoline when you get off. Washing sticks together after being tumble-dried. A light bulb working. 2. Fill in the gaps in the following sentences. Rubbing two i ( substances that do not conduct electricity ) together sometimes rubs off e from one substance to the other. If enough c is rubbed off the e can jump back and a s is seen or heard. Before the spark jumps each item is carrying s e. The moving electrons in the spark are forming a current of electricity.

4 Insulators and Conductors 1. Fill in the gaps in the following sentences. A substance that allows e to flow through it is a c. A substance that does not allow e to flow through it is an i. 2. Identify the following substances by writing conductor or insulator under each picture. 3. Fill in the gaps in the following sentences explaining why conductors conduct and insulators insulate. The e that surround every atom are held very tightly by the atoms in an i and can not move from their position orbiting their own a. They don t co e. The e in a c are able to move freely from their own atom. When e move the material c electricity. 3. When two differently charged objects are placed close to one another two things can happen; they either attract or repel one another. Draw arrows on the three diagrams below showing wether the objects attract or repel each other and then complete the general rule that follows. + + Different charges = Unlike charges + Same charges = Like charges General Rule L charges R U charges A

5 Current, Circuits and Components 1. A battery supplies energy and electrons for a current. It has both a n terminal (Minus a bit ) and a p terminal (Plus a bit ). If a wire is connected between them electrons (ne ch ) are at toward the p terminal and more e are supplied by the battery at the n terminal. A cu flows in the wire. The direction of C C is in the o direction toward the n terminal and is given an arrow on the circuit below. 2. Fill in the correct names and copy out and learn the symbols for the following electrical circuit components. Picture Symbol Name Symbol l or b o c + _ b s c b s r A a V v L E D D f t w j t w c not j

6 ACROSS 2. The negatively charged part of an atom that orbit the nucleus 3. Type of electricity involving charged particles that are stationary on an object (2 words 6,11) 5. Components wired one after the other in a circuit are wired in 9. A substance that doesn t allow the flow of current through it 10. The unit of resistance 13. A device that measures the energy gain or loss across a component so is wired in parallel 14. The loss or gain of energy by electrons 15. The property of a substance that makes it hard for electrons to flow through it DOWN 1. The name for an atom that has equal numbers of positive and negative particles 4. The movement of charged particles 6. The direction a positive particle would move in a circuit the opposite of electron movement ( current) 7. A substance that allows current to flow through it 8. A device that measures the amount of current passing through it (in Amps) 11. A component that only allow current to flow in one direction 12. A number of cells in series

7 Series Circuits 1. Fill in the gaps in the following sentences that practice the rules you use when drawing circuits. i) C are connected together using w. The w are ruled straight. ii) C diagrams have sq corners ( 90 0 ). iii) C d never have components drawn in the corners. iv) C d have lines ruled that c the components to each other (there are no gaps) 2. Practice drawing the following circuits using the rules above and remembering the symbols for each component. A V

8 Parallel and Series Circuits a comparison. Draw the circuits in the boxes below the description of them and then answer the questions that follow.( remember that in a series on TV one episode follows another on the same channel- same wire, Railway tracks run parallel to each other, beside each other) 1. A two cell battery with two light bulbs in series completing the circuit. 2. A two cell battery with two light bulbs wired in parallel to each other. If there had been only one light bulb in the circuit above would it have been the same, brighter or dimmer? Do both light bulbs have the same brightness? If one of the light bulbs was unscrewed so it went out, what would happen to the other one? A set of cheap Christmas lights blew one bulb and the whole string went out. How do you think they were wired? 3. In the box below draw the circuit described and then work out the voltage the battery must be supplying to the current to push it through the stated resistance. (V = I R ) A 6 cell battery is wired to a resistor, a switch, a 35 Ohm resistor with an ammeter that reads 4.6 Amps when the switch is closed. A voltmeter is wired in to measure the voltage across the resistor. If there had been only one light bulb in the circuit above would it have been the same, brighter or dimmer? Do both light bulbs have the same brightness? If one of the light bulbs was unscrewed so it went out, what would happen to the other one? A set of better Christmas lights blew one bulb and the whole string did not go out. How do you think they were wired? 4. In the box below draw the circuit described. A three cell battery is wired to an ammeter, a light bulb and a switch in series. Then two 20 Ohm resistors are wired in parallel to each other to complete the circuit. A voltmeter measures the voltage drop across the light bulb only. The Voltmeter would read

9 Safe electrical practice in and around the home. 1. The diagram below shows a lot of idiotic behaviour that can occur when electricity is fooled around with by people who don t seem to realise that it kills. How many stupid things can you identify? Record them under the picture. Get some other person to help you if you can not identify nine things( there are at least 10). They might learn a lifesaving tip or two as well. metal knife 1. If you suspect some one has been electrocuted, what don t you do? 4. Why is the bloke prodding the victim with a dry stick?

10 Definitions Practice In the space beside each of the words in the following list, select a definition from the list below and write it out. ammeter battery of cells conductor Conventional Current diode electron current insulator neutral atom ohm resistance static electricity voltage voltmeter series circuits Definitions List a b c d e f g h i j k l m n o The direction a positive charge would move in and electrons move in the opposite direction A device that measures the amount of current passing through it in Amps. Movement or flow of charged particles A series of individual cells that store electrical energy on charged particles. A component in a circuit that only lets electricity flow in one direction. A substance that allows an electrical current to flow. A substance that does not permit the flow of current through it. The type of electricity when charged particles are stationary on an object. The negatively charged particle that orbits the nucleus of atoms and is responsible for electricity. Property of a substance which makes it hard for electrons to pass through it. The amount of energy gained or lost by electric charges. Components are wired one after the other on the same circuit. An atom that has an equal number of positively charged protons and negatively charged electrons A device that measures the change in energy of a current so must be wired in Parallel The unit that resistance of a component is measured in.