PICK UP: Papers & Calc. TURN IN: - (orange sheet if you did not yesterday) DO NOW: On a half-sheet, draw the schematic for the following circuit.

Transcription

1 PICK UP: Papers & Calc HW: U7-9 (green) Next Test: QUIZ TOMORROW Exam 7 on 3/28 TURN IN: - (orange sheet if you did not yesterday) DO NOW: On a half-sheet, draw the schematic for the following circuit.

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3 By the end of the day today, IWBAT show how power, current, potential difference, and resistance are mathematically related. Why it matters in LIFE: Part of being a functional human being is being able to understand what s happening in the world around you! Why it matters in THIS CLASS: Our Goal = 80% Mastering today s lesson (focused participation, asking questions, etc) is the first brick that will help us reach our goal for this unit, and eventually for the year

4 TEKS: 5(C) describe and calculate how the magnitude of the electrical force between two objects depends on their charges and the distance between them By the end of today, IWBAT draw simple circuit diagrams and indicate the direction of conventional current flow. show how power, current, potential difference, and resistance are mathematically related. Topic: Simple Circuits

5 ELECTRICITY THE FLOW OF CHARGE

6 CLOSED CIRCUIT A complete and unbroken conducting path between the source of the current and the return of the current

7 OPEN CIRCUIT A circuit with a switch turned to the off position, or a circuit with any break in it (electricity cannot travel through an open circuit)

8 CIRCUIT SCHEMATIC SYMBOLS Current Resistance Voltage wire

9 CURRENT FLOW

10 ELECTRICITY FLOWS LIKE WATER

11 CURRENT, I (Units of amps (A)) Current wire The flow of charge through a circuit. Ammeters measure current.

12 AMMETERS MEASURE CURRENT Would you get a reading? A Yes! The circuit is closed, so current is flowing. A No! The circuit is open, so current is not flowing. Reads I = zero.

13 RESISTANCE, R (Units of ohms (Ω)) Resistance A material s ability to resist (restrict) the flow of electricity.

14 VOLTAGE, V (Units of volts (V)) Voltage (Electric Potential Difference) The electrical pressure that causes charges to move created by a difference and separation of charge. Voltmeters measure voltage.

15 VOCAB CARDS LIGHTNING ROUND!

16 VOLTAGE, CURRENT, RESISTANCE V = I R V = Voltage (volts, V) I = Current (amps, A) R = Resistance (ohms, Ω)

17 ELECTRICAL POWER, P (Units watts (W)) P = V I P = Electrical Power (watts, W) V = Voltage (volts, V) I = Current (amps, A)

18 TABLE OF VARIABLES & UNITS Variable Symbol Units (Word) Units (Symbol) Current I amps A Resistance R ohms Ω Voltage V volts V Power P watts W

19 EXAMPLE #1 A 12 V battery causes a 3 amp current through a light bulb. a) What is the resistance of the light bulb? b) How much power does it draw?

20 EXAMPLE #1 A 12 V battery causes a 3 amp current through a light bulb. a) What is the resistance of the light bulb? b) How much power does it draw? G: V = 12 V I = 3 A U: R =? E: I = V/R R = V/I S: R = 12/3 R = 4 ohms G: V = 12 V I = 3 A U: P =? E: P = VI S: P = 12*3 P = 36 watts

21 Do GP #1 with your table partner!

22 EXAMPLE #2 A light bulb in a circuit with a 12 V battery uses 24 watts. What is the resistance of the light bulb?

23 EXAMPLE #2 A light bulb in a circuit with a 12 V battery uses 24 watts. What is the resistance of the light bulb? G: V = 12 V P = 24 W U: R =? I =? E: I = V/R R = V/I P = VI I = P/V S: I = 24W / 12 V = 2 amps R = 12 V / 2 A = 6 ohms R = 6 ohms

24 Do GP #2 with your table partner!

25 EXAMPLE #3 In a circuit, what happens to the current if the voltage is tripled and the resistance remains the same?

26 EXAMPLE #3 In a circuit, what happens to the current if the voltage is tripled and the resistance remains the same? G: V = tripled = x 3 R = constant U: I =? E: I = V/R S: I = x 3/1 I = x 3 The current in the circuit is tripled! Aka the new current is 3 times as big as the old current; 3I

27 Do GP #3 & 4 with your table partner!

28 INDEPENDENT PRACTICE! Procedure for IP time: 1) Silent work time 2) Try and solve without notes first! Hierarchy of who to ask 1) Your brain 2) Your notes 3) Ms. Kelly (after you #embracethestruggle)

29 EXIT TICKET 1. In a circuit, what happens to power if resistance is doubled and voltage remains the same? 2. A light bulb in a circuit with a 36 V battery uses 72 watts. What is the resistance of the light bulb?

30 EXIT TICKET 1. The power is cut in half 2. R = 18 ohms G: V = constant R = doubled = * 2 U: P =? E: I = V/R I = constant/2 = * ½ P = VI P = constant* ½ = * ½ The power is cut in half! The new power is ½ of the original power. G: V = 36 V P = 72 W U: R =? I =? E: I = V/R R = V/I P = VI I = P/V S: I = 72W / 36 V = 2 amps R = 36 V / 2 A = 18 ohms R = 18 ohms

31 ON THE BACK OF YOUR E.T. 1. What was one strength of yours from today? 2. What was one weakness of yours from today? 3. What was one strength of mine from today? 4. What was one strength of mine from today?