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Name: ____________________________________________ Group: __________ Support activities – Second Year of Secondary Cycle Two ACTIVITY 22 ANSWER KEY Date: __________________ EST STUDENT BOOK: Chapter 5, pages 156–163 RELATED HANDOUT: Concept review 22 Electrical circuits 1. Complete the following sentences, using the words or groups of words in the box below. You may use some words more than once. • • • • • • • • adds up branch out charges circuit circuit breakers conservation of charge conservation of energy continues to flow • • • • • • • • conventional current current intensity diagrams electrical energy equal to equivalent resistance flow • • • • • • • • motion negative node parallel positive potential power supply reduces • • • • • • • • resistors series shared single total energy acquired total energy transferred value wires flow a) For charges to ________________________ , they must be able to move in a loop like a racetrack. A circuit provides them with a loop to flow through, and a power supply keeps motion circuit them in ________________________ . Any ________________________ must contain at power supply least the following three components: a ________________________ to create a potential electrical energy difference, one or more elements that use _______________________ (for example, a light © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. wires bulb), and ________________________ that connect the elements and the power supply. diagrams b) Symbols and ________________________ are often used to represent electrical circuits. conventional The current is shown in the ________________________ current direction, in other words, positive negative from the _______________________ terminal to the _______________________ terminal. Series parallel c) ________________________ circuits and ________________________ circuits are two ways of connecting the components of an electrical circuit. series d) In a ____________________ circuit, the components are connected end to end. The circuit branch out does not ____________________ , which means that all the charges follow the same path. current If one of the circuit components is defective, the ______________________ ceases to flow. adds up The energy used by each of the resistors ______________________ . Adding resistors reduces _____________________ the energy available for each one. Fuses and series circuit breakers ____________________ are examples of elements connected in ____________________ . Observatory / Guide 11129-B 1 ANSWER KEY Support activities – SecondYear of Secondary Cycle Two ACTIVITY 22 Electrical circuits Name: ____________________________________________ Group: __________ Date: __________________ parallel e) A________________________ circuit branches out in at least one place. The charges ________________________ can therefore take different paths. The point at which a circuit node separates into two paths is called a “________________________ .” If an element of the continues to flow circuit is defective, the current ________________________ through the elements in the reduces other branches. Adding resistors ________________________ the total resistance. The shared current intensity is ________________________ among the various resistors. f) EST Two important laws in electricity are based on the law of conservation of charge _______________________ conservation of energy and the law of ________________________ . Kirchhoff’s first law states that the current intensity ________________________ flowing into an element or a node of an electrical circuit is equal to always ________________________ the current intensity flowing out of it. Kirchhoff’s total energy acquired second law is about potential difference. It states that the ________________________ by total energy transferred the charges from the power supply is always equal to the ________________________ by these charges, whatever pathway they may take in the circuit. series g) EST Kirchhoff’s two laws can be summarized as follows: In a _______________________ circuit, the total current intensity is equal to the current that flows through each of the resistors ________________________ , and the total potential difference is equal to the sum of the parallel potential differences of all the resistors in the circuit. In a ________________________ circuit, the total intensity is equal to the sum of the currents flowing through each of the potential resistors in the circuit, and the total ________________________ difference is the same © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. everywhere, for each element in the circuit. h) EST The following equations represent Kirchhoff’s two laws: series For a ________________________ circuit: Itotal I1 I2 I3 I4 … Vtotal V1 + V2 + V3 + V4 + … parallel For a ________________________ circuit: Itotal I1 + I2 + I3 + I4 + … Vtotal V1 V2 V3 V4 … i) equivalent resistance , symbolized by the letters Req, is equal EST The ________________________ to the resistance value needed to replace all the resistors in a circuit with a single ________________________ resistor. By applying Ohm’s law and Kirchhoff’s laws, this value ________________________ can be calculated with the following equations: Observatory / Guide 11129-B 2 ANSWER KEY Support activities – SecondYear of Secondary Cycle Two ACTIVITY 22 Electrical circuits Name: ____________________________________________ Group: __________ Date: __________________ series For a ________________________ circuit: Req R1 + R2 + R3 + R4 + … 1 parallel For a ________________________ circuit: Req = 1 1 1 + + +… R1 R2 R3 2. Draw a series circuit and a parallel circuit that each include a power supply, two light bulbs and two resistors. Answers will vary. Examples: a) series circuit b) parallel circuit 3. Calculate the resistance value in the circuit below. In a series circuit, V = RI V I 100 V R= 2A R = 50 Ω © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. R= 4. EST Calculate the current intensity flowing through the R1 resistor in the circuit below. In a series circuit, the current intensity is the same everywhere. Consequently, R1 = 10 A. Observatory / Guide 11129-B 3 ANSWER KEY Support activities – SecondYear of Secondary Cycle Two ACTIVITY 22 Electrical circuits Name: ____________________________________________ Group: __________ Date: __________________ 5. EST In the circuit below, what is the potential difference at the terminals of the power supply? In a parallel circuit, the potential difference is the same everywhere. At the power supply terminals, it y différence deV. potentiel est égale partout. Aux bornes de la source, elle isalso therefore also 80 6. EST In the table below, write the equations that express the application of Ohm’s law and Kirchhoff’s laws to series and parallel circuits. Characteristic Current intensity Potential difference Equivalent resistance Series circuit Parallel circuit Itotal = I1 = I2 = I3 = I4 = … Itotal = I1 + I2 + I3 + I4 + … Vtotal = V1 + V2 + V3 + V4 + … Vtotal = V1 = V2 = V3 = V4 = … 1 Req = R1 + R2 + R3 + R4 + … Req = 1 1 1 + + +… R3 R2 R1 7. EST Calculate the equivalent resistance in each of the following three circuits. © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. a) Series circuit: Req = R1 + R2 + R3 = 100 Ω + 50 Ω + 30 Ω = 180 Ω Parallel circuit: Req = b) Req = 1 1 1 + R1 R2 1 1 1 + 50 Ω 50 Ω Req = 25 Ω Observatory / Guide 11129-B 4 ANSWER KEY Support activities – SecondYear of Secondary Cycle Two ACTIVITY 22 Electrical circuits Name: ____________________________________________ Group: __________ Date: __________________ c) Parallel circuit: Req = Req = 1 1 1 1 + + R1 R2 R3 1 1 1 1 + + 100 Ω 25 Ω 75 Ω © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. Req = 15.78 Ω Observatory / Guide 11129-B 5 ANSWER KEY Support activities – SecondYear of Secondary Cycle Two ACTIVITY 22 Electrical circuits