September 7, 2017 Resistance Length of Wire Affects Resistance

Drill – Mini Quiz – 10 points Copy down today’s objective onto your drill sheet. Write “quiz” in the box for the drill. Clear your desk except for a piece of paper + pencil.

Quiz – You’ve Got This! Name the three components of a circuit. The electrons in a circuit flow from the __________ terminal of the battery to the ____________ terminal of the battery. Conventionally, the current flow in a circuit is represented as flowing from the __________ terminal of the battery to the ____________ terminal of the battery. Draw a circuit diagram containing 2 batteries and 2 lightbulbs. Draw the path of the current flowing from each battery.

Resistance (R) Resistance = the opposition of a material to the flow of electric current. Unit = Ohm (Ω) 1 Ω = the resistance permitting an electric charge of 1 A (amp) to flow when 1 V (volt) is applied. Rank the following materials in order from low resistance to high resistance: glass rod, copper wire, aluminum foil.

Resistors Device designed to have a specified resistance. Constructed of metal wire, graphite, or semiconductors, and engineered to maintain a stable resistance value. Produce heat as electric power is dissipated by them in a circuit.

Purpose of Resistors Resistors are used to reduce the available voltage or current flow in a circuit or section of a circuit. Depending on the location of the resistors, resistors can divide current/voltage within a circuit. This can be useful if electrical loads within the same circuit require different amounts of current/voltage.

Other Sources of Resistance Resistance in an electric circuit is not only provided by the resistor, but also from the wires. Four factors affect resistance of wires Length Cross-sectional area Temperature Material

Resistance Lab – Day 1 Objective: Determine the effect of length on the resistance of a wire. Materials: spool of kanthal wire, multimeter, ruler, scissors. Take note of the materials used, procedures, and data in your notebook. You will need this information for the Lab Report.

Multimeter Record the ”gauge” of your wire (written on spool). Set multimeter to 200 Ω (green section). Twist end of wire (2-3 turns) around each probe. Pull wire taut. Keep hands steady or you will not get a proper reading. When reading stabilizes, record resistance value. Test 4 lengths of wire.

September 8, 2017 Resistance Cross-Sectional Area Affects Resistance

Drill – 4 minutes, Open Note What is the definition of resistance? Name two real-life uses of resistors. What are four factors affecting resistance.

Resistance Lab – Part 1 Objective: Determine the effect of length on the resistance of a wire. Materials: spool of kanthal wire, multimeter, ruler, scissors. Take note of the materials used, procedures, and data in your notebook. You will need this information for the Lab Report.

Multimeter Record the ”gauge” of your wire (written on spool). Set multimeter to 200 Ω (green section). Twist end of wire (2-3 turns) around each probe. Pull wire taut. Keep hands steady or you will not get a proper reading. When reading stabilizes, record resistance value. Test 4 lengths of wire.

Resistance Lab – Part 2 Objective: Determine the effect of cross-sectional area on the resistance of a wire. Materials: spool of kanthal wire, multimeter, ruler, scissors. Take note of the materials used, procedures, and data in your notebook. You will need this information for the Lab Report. Test 4 wires of varying cross-sectional area.

Lab Report requirements + organization Typed or pen (with few mistakes). Include both labs within one report. Part 1 = Length Part 2 = Cross-sectional Area Results: Include data collected Analysis: Include graphs + mathematical equation. Conclusion: Explain the relationships between factor and effect on resistance.

Due Dates Monday = first draft for peer review Wednesday = final copy