Students will need about 30 minutes to complete these constructed response tasks.

Transcription

1 Electric Title of Circuits Concept Constructed Response Teacher Guide Students will need about 30 minutes to complete these constructed response tasks. Objectives assessed: Understand the functions of common elements that make up series and parallel circuits and interpret circuit diagrams. Understand that resistors in DC circuits increase in temperature because they dissipate energy. Explain how the characteristics of transistors make them useful in electric circuits.. The symbols for some common elements that make up series and parallel circuits are shown below. Complete the table below. In the first column, fill in the names of the circuit elements. In the second column, draw in the corresponding symbols. Brief Constructed Response: Name of Concept Page of 8

2 5 Solution includes all correct table responses. 4 Solution includes at least ten correct table responses. 3 Solution includes at least eight correct table responses. 2 Solution includes at least six correct table responses. Solution includes at least four correct table responses. Objectives assessed: Predict the voltage or current in a simple DC circuit that includes wires, resistors, capacitors, and batteries. 2. Consider the following circuit diagram: Brief Constructed Response: Name of Concept Page 2 of 8

3 Draw the general shape of the graph of the current in the circuit over time. Draw the general shape of the graph of the charge on the capacitor over time. 3 Both graphs show correct general exponential shape. 2 One graph shows correct general exponential shape. Both graphs incorrect, but the student shows the basic understanding that the first graph is decreasing and the second graph is increasing. Brief Constructed Response: Name of Concept Page 3 of 8

4 Objectives assessed: Use Ohm's law to describe the relationship between current, voltage, and resistance. Explain the relationship between electrical power, current, and voltage. Solve problems involving power in resistive circuit elements. For both series and parallel circuits, calculate the current, potential difference, resistance, and power of different circuit elements. Design and build both series and parallel circuits. 3. A 2-V battery is connected in series with resistor R = 2 Ω and resistor R 2 = 4.0 Ω. Draw the circuit diagram and label it with each component. Find the equivalent resistance. Find the total current in the circuit. Find the current through each resistor. Find the power in each resistor and in the circuit. [Art: Start with circuit diagram below, with 2 V battery at left, with 2 Ω and 4 Ω resistors in series. We DO NOT own this art, so use the art below only as a starting point. Omit the current arrow, use only two resistors, and make the battery look like the battery in the diagram for Question 4. Also omit the green squiggly E label] R eq = R + R 2 = 2 Ω Ω = 6 Ω I = V = 2 V R tot 6 Ω = 0.75 A P circuit = IV = ( 0.75 A) ( 2 V)= 9.0 W V = IR = ( 0.75 A) ( 2 Ω)= 9.0 V P = IV = ( 0.75 A) ( 9.0 V)= 6.75 W V 2 = IR 2 = ( 0.75 A) ( 4.0 Ω)= 3.0 V P 2 = IV 2 = ( 0.75 A) ( 3.0 V)= 2.25 W Brief Constructed Response: Name of Concept Page 4 of 8

5 4 All of: draws correct circuit diagram; finds correct total resistance; finds correct circuit current; finds correct power. 3 Three of: draws correct circuit diagram; finds correct total resistance; finds correct circuit current; finds correct power. Allow points for correct calculations using incorrect values found earlier. 2 Two of: draws correct circuit diagram; finds correct total resistance; finds correct circuit current; finds correct power. Allow points for correct calculations using incorrect values found earlier. One of: draws correct circuit diagram; finds correct total resistance; finds correct circuit current; finds correct power. Allow points for correct calculations using incorrect values found earlier. 4. A 2-V battery is connected in parallel with resistor R = 2 Ω and resistor R 2 = 4.0 Ω. Draw the circuit diagram and label it with each component. Find the equivalent resistance. Find the total current in the circuit. Find the current through each resistor. Find the power in the circuit. = R eq 2 Ω Ω = 3.0 Ω R eq = 3.0 Ω I = V R eq = 2 V 3.0 Ω = 4.0 A I = V R = 2 V 2 Ω =.0 A I 2 = V = 2 V R Ω = 3.0 A P = IV = 4.0 A ( )( 2 V) = 48 W Brief Constructed Response: Name of Concept Page 5 of 8

6 5 All of: draws correct circuit diagram; finds correct equivalent resistance; finds correct total circuit current; finds correct current through each resistor; finds correct power. 4 Four of: draws correct circuit diagram; finds correct equivalent resistance; finds correct total circuit current; finds correct current through each resistor; finds correct power. Allow points for correct calculations using incorrect values found earlier. 3 Three of: draws correct circuit diagram; finds correct equivalent resistance; finds correct total circuit current; finds correct current through each resistor; finds correct power. Allow points for correct calculations using incorrect values found earlier. 2 Two of: draws correct circuit diagram; finds correct equivalent resistance; finds correct total circuit current; finds correct current through each resistor; finds correct power. Allow points for correct calculations using incorrect values found earlier. One of: draws correct circuit diagram; finds correct equivalent resistance; finds correct total circuit current; finds correct current through each resistor; finds correct power. Allow points for correct calculations using incorrect values found earlier. Brief Constructed Response: Name of Concept Page 6 of 8

7 5. You have a 2 V battery, a R = 2 Ω resistor, and another component that requires a current of 2.0 A and a voltage drop of 6.0 V. What value of resistor would you connect in parallel with R, with both resistors in series with the other component, to produce the required current and voltage drop? Voltage drop across resistors in parallel = 2 V 6 V = 6 V Equivalent resistance R eq for parallel resistors: R eq = 6.0 V 2.0 A = 3.0 Ω = R eq 2 Ω + R 2 R 2 = R eq 2 Ω R 2 = 3.0 Ω 2 Ω R 2 = 4.0 Ω 3 Calculates voltage drop across resistors, figures equivalent resistance of parallel resistors, calculates R 2. 2 Calculates voltage drop across resistors, figures equivalent resistance of parallel resistors. Allow points for correct calculations using incorrect values found earlier. Calculates voltage drop across resistors. Allow points for correct calculations using incorrect values found earlier. Brief Constructed Response: Name of Concept Page 7 of 8

8 6. You have a battery with leads B and B 2, an open switch with ends S and S 2, and two resistors R A and R B with ends R A and R A2, and R B and R B2. Which ends would you connect together to make a circuit with connected in parallel with the battery, and why do you use the switch? Draw a picture of the circuit that would result. [Art: Start with the circuit diagram given in the Correct Response to Question 4, and omit voltage and resistance value labels. Add an open switch above and to the right of the battery (i.e., above and to the left of the resistors), and label component ends as discussed in the answer to Question 6. Component end labels will juxtapose at connections between components. Place labels in close proximity to juxtapositions.] Connect open switch end S to battery lead B, ends R A and R B to S 2, and ends R A2 and R B2 to B 2. The switch is used for safety, so that electricity doesn t flow in the circuit until we activate it. 3 Draws correct circuit diagram, knows why open switch is used. 2 Draws correct circuit diagram, but does not answer about open switch Draws incorrect circuit diagram Brief Constructed Response: Name of Concept Page 8 of 8