Italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included to support the teacher’s understanding of the content being introduced within the CELL.

ASK WHY

Remind students that electricity is important because it is the most common energy we consume and depend on in our daily lives. We use electrically powered gadgets to communicate, for entertainment, to produce food, and to run our homes. Electricity is even starting to transform our transportation systems.

BRANCH OUT

Remind students that solar energy systems engineers design solar panels that convert the sun’s energy into electricity that will then be used to power systems such as hot water, space heating systems, or put electricity into the grid.

GET FOCUSED

GO DEEPER

As a class, read the Background(s) in the Investigation. Have students read the information aloud or silently to themselves. When students have finished, discuss the following concepts as a class:

• Magnetism is a property of matter.
• Temporary magnets are created by wrapping a coil of wire around a piece of metal and passing an electric current through the wire. 
• This type of magnet is called an electromagnet.
• The strength of an electromagnet is determined by the size of the magnetic field. 
• A magnetic field (B) can be calculated using the following formula:

B = μ₀ × n × I

• This formula can be read as follows: “B is equal to mu sub zero multiplied by n multiplied by I.”
• In the formula, each letter represents something different.
  • B = magnetic field
  • μ0 = 4π × 10^-7 Tesla-meters/amps. This number is a constant and does not change when making calculations. For your calculations, use μ0 = 12.57 x 10^-7
  • n = N/L (N = number of turns of wire
  • L = length of the coil)
  • I = current in amps
• A magnetic field is reported in units of Tesla, which is abbreviated with the letter “T”.

Note: These concepts are integrated into the Background(s) and are used to deepen students’ comprehension of the big ideas.

LEARN THE LabLearner LINGO

The following Key Term is introduced in the Investigation Background(s). It should be used, as appropriate, by teachers and students during everyday classroom discourse.

• Tesla (T)

Note: The definitions of this term can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.

SET FOR SUCCESS

• As a class, briefly summarize what was learned in Investigations One and Two.

Note: In Investigation One, the current was increased in a circuit by increasing the number of batteries in the circuit. The increase in current was proportional to the increase in voltage. When the resistor in the circuit was changed, the amount of current also increased, but by a smaller amount than in the first circuit. However, this increase was also proportional to the increase in voltage. In Investigation Two, increasing resistance in a circuit with constant voltage caused the current to decrease. In addition, the length of a resistor was increased causing a decrease in current. In contrast, increasing the cross-sectional area of a resistor caused the current to increase.

• Ask students to explain why current decreased when resistance increased in Investigation Two in terms of Ohm’s Law.

Note: Resistance is the ratio of voltage to current. When voltage is held constant, increasing the amount of resistance in a circuit causes the current to decrease.

• Ask students why placing two 1000 Ω resistors in series caused a decrease in the amount of current.

Note: Placing two 1000 Ω resistors in series had the same effect as increasing the length of a resistor. Increasing the length of a resistor causes a decrease in current because the flow of electrons through the resistor is slowed for a longer period of time.

• Ask students why placing two 1000 Ω resistors in parallel caused an increase in the amount of current.

Note: Placing two 1000 Ω resistors in parallel had the same effect as increasing the diameter of a resistor. The increasing diameter increases the cross-sectional area of a resistor. Increasing cross-sectional area decreases the amount of resistance provided by a resistor by providing more possible paths for electrons, thus allowing more electrons to flow through the resistor at the same time. This increases the flow of current.

• Direct students to complete the Recall section in their SDRs. Student answers may vary.

• What is a magnetic field?
• What is an electromagnet?

• Play the video below. Stop to ask students questions or answer students’ questions when necessary. Remind students to follow along with their SDRs and make any notes that they think might be helpful.
• After the video, direct students to divide into their lab groups to discuss their strategy for the lab. For example, they may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow students to anticipate the laboratory experience they will soon encounter. Students should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.

HOMEWORK

Tell students that they should review the Investigation in preparation for the Lab.