INVESTIGATION 1 I-CHECK ENERGY

A group of students in another class needs your help. They want to design a switch to control a circuit that runs a motor. The materials that were available were a thin sheet of copper, brass fasteners, and a paper clip. They used the materials as you see in the diagram. When they put the switch into the circuit with the D-cell and motor, the motor spun all the time. No matter what position the switch was in, open or closed, the motor kept spinning. What is the most likely problem with the switch?

• The switch is not connected to the circuit.

• The switch is made of non-conductive materials.

• The switch is always making contact, so the circuit is always closed.

• The motor is faulty and ignores the switch.

How would you improve the design of the switch so that the students can use it to turn the motor on and off?

• Use an insulating material to separate the copper sheet and paper clip when the switch is open.

• Connect the motor directly to the D-cell without a switch.

• Replace the copper sheet with a plastic sheet.

• Remove the brass fasteners from the circuit.

One of the people who works in the city office says, “There is one more thing you should think about. Some lightbulbs get hotter than others. In the summer, hot bulbs make our office even warmer.” Which plan would be the best fair test to find out how room temperature is affected by the different kinds of bulbs?

• Put a different kind of bulb in three lamps in the same room and check the air temperature.

• Put a lamp with an LED bulb in a small room, a lamp with a CFL bulb in a medium-sized room, and an incandescent bulb in a large room. Check the air temperature in each room after an hour.

• Put bulbs in three lamps, a different kind of bulb in each lamp. Place the lamps in three rooms the same size and measure the temperature each hour of the work day.

• Check the air temperature of rooms with different kinds of bulbs at different times of day.

Evaluate the drawing and explain why the student has or has not met the design criteria.

• The student has met the design criteria.

• The student has not met the design criteria.

Next week’s temperature is predicted to be hot. You find an old fan in the garage and want to find out if it still works. Which actions would provide evidence that the fan is still working?

• The blades of the fan are turning: Y The fan is making a humming sound: Y

• The fan is covered in dust: N The fan is missing a blade: N

• The fan is plugged into an electric socket: N The switch on the fan is in the ON position: N

• The fan is not moving and is silent: N The fan is unplugged: N

Four students presented their models showing how electricity flows through a circuit. Which picture and description best explains why the motor runs?

• [Diagram] Electricity flows from the negative terminal of the D-cell to the motor and then to the positive terminal of the D-cell.

• [Diagram] Electricity flows from the motor to both terminals of the D-cell.

• [Diagram] Electricity flows from both terminals of the D-cell to the motor.

• [Diagram] Electricity flows from the positive terminal of the D-cell to the motor and then to the negative terminal of the D-cell.

A student wants to complete this circuit so the motor will run. She has only a few materials available. What can she use to close the circuit between the D-cell and the switch?

• A piece of string

• Aluminum foil

• Plastic straws

• Wooden craft sticks