Grade 11 - Resistance (Electrical Systems - Circuits)

PRESCRIBED LEARNING OUTCOMES

• construct circuits with two or more resistors in series and in parallel
• define equivalent resistance
• compare the equivalent resistance of like resistors in a series circuit and in a parallel circuit
• describe the effect on total current in a circuit when more resistors are added in series and in parallel
• calculate the equivalent resistance when at least three resistors are placed in series and parallel combinations
• use a multimeter to measure the resistance of various loads
• determine the value of resistors used in electrical circuits by referring to colour-code charts

SUGGESTED INSTRUCTIONAL STRATEGIES

• Ask each student to build a series, a parallel, and a series-parallel circuit, using a power source, three identical light bulbs, wires, and a switch. Ask each student to remove a light bulb and observe the effect on the total circuit current in both series and parallel circuits.
• Have students use ohmmeters to identify the effective resistance of various series and parallel resistance combinations and discuss the results.
• Ask each student to measure human body resistance by holding a multimeter lead in each hand. Students do this once with wet hands and once with dry hands and observe how this difference affects resistance. Using a chart showing the effects of current on the human body, they calculate the voltages needed in different circumstances to produce muscle spasms.
• Provide students with multi-resistor circuit diagrams and have them calculate the equivalent resistance of circuit branches and entire circuits.
• Obtain out-of-service equipment and ask students to dismantle the devices in the classroom. This gives them opportunities to use tools such as needle-nose pliers and soldering guns. Help students identify resistors in the circuit boards. Have them detach selected resistors, tape these to sheets of paper, write the resistance values beside each, and then use multimeters to check the colour-coded values.

SUGGESTED ASSESSMENT STRATEGIES

• As students work on circuit constructions and investigations, probe their understanding by asking them to:
  • identify the series and parallel portions of circuits
  • propose methods of reducing resistance with constant current or voltage
  • propose methods of increasing current for fixed voltage or resistance
  • determine and use equivalent resistance
  Note the extent to which their responses indicate understanding of relationships between resistance, voltage, and current.
• Have students in groups research and report on medical applications such as electrocardiograms, electroencephalograms, TENS, and defibrillation units. Assess the reports using criteria such as the extent to which students can identify:
  • resistance in the human body
  • electrical sources in the body
  • current restrictions
  • maximum voltage that can be applied and possible effects if exceeded
• Form pairs or small groups and ask each to design a DC electrical system for the following:
  • doorbell for people who are deaf
  • bedroom bell for security
  • phone light for people who are deaf
  • electronic locker key
  Criteria to assess the designs might include:
  • feasibility (e.g., cost, availability of components)
  • practicality of design (e.g., size, durability)
  • identification of factors such as voltage, current, and time
  • application of series and parallel circuits
  • appropriate use of resistors

RECOMMENDED LEARNING RESOURCES

Applications of Physics 11 and 12 develops an understanding of the concepts of physics through the design, construction, and use of a variety of devices. Although the resources listed below provide a range of teaching and learning opportunities in physics, none of them provide a comprehensive resources package that completely supports the philosophy and approach of the British Columbia curriculum in the applications of physics. Please see the Appendix B Introduction for further information.

Print Materials

• Cambridge Coordinated Science: Physics
• Conceptual Physics, Third Edition
• Heinemann Advanced Science: Physics
• Physics: Principles and Problems, American Edition
• Physics: Principles and Problems, Canadian Edition

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Last Modified: April 1, 1998.
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