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ELECTROMAGNETS on e Activity Sheet EEM-12A Objectives: To explore electric circuits in order to explain how they relate to magnetic fields. ENERGY Note: Are electricity and magnetism related? Materials (per group) 1 box of paper clips compass 2 D cell battery holders 2 D cell batteries (1.5 V) magnet switch Activity 1: Exploring a Compass 1. Take the magnet and the compass. Hold them about 30 cm apart. 2. Slowly move the compass closer to the magnet. Record your observations. Repeat if necessary. _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ Activity 2: Circuits and Compasses 3. Construct a simple circuit using the provided materials. (Just a cell wired to a switch) Leave the switch open. 4. Place the compass near the circuit. Record your observations in the left half of Figure 1, “Compass Observations.” (Draw the compass needle.) 5. Close the switch. Record your observations in the right half of Figure 1, “Compass Observations.” FIGURE 1 COMPASS OBSERVATIONS OPEN CLOSED N N W E S W E S 6. Explain the movement of the compass needle after the wire was connected to the circuit. Use your observations and prior knowledge about the effects of magnets on compass needles to support your answer. _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ The observations you just made represent one of the biggest blunders in the history of science. However, this blunder has revolutionized technology and enabled scientists to develop devices that convert electrical energy into mechanical energy. 7. Read notate the passage, “Oersted’s Surprise.” OERSTED’S SURPRISE Many of the greatest scientific discoveries have been lucky accidents. Electromagnetism was one of those. During a lecture in the year 1819, Hans Oersted had a compass sitting next to a wire. When Oersted completed the circuit by connecting the wire to a battery, the direction that the needle was pointing changed. This indicated that the electricity flowing through the wire had created a magnetic field. When he stopped the flow of electricity, the compass needle returned to its original position. Although most scientists are pleased by these unexpected discoveries, Hans Oersted was not. His lecture that day was supposed to demonstrate that electricity and Figure 1 magnetism have absolutely nothing to do with each other. Solenoid André Ampere followed up on this discovery and found that two parallel wires carrying electric currents running the same direction attracted each other. This observation led to the creation of a solenoid or coil as shown in Figure 1. In the solenoid, the magnetic field created by a loop of wire carrying an electric current joins together with the magnetic fields from other coils of wire to create more powerful magnetic force. This magnetic field only lasts as long as the electric current is flowing through the coils of wire. It has been found that the overall strength of the field could be further amplified by inserting a ferrous (iron containing) core into the center of the wire loops. This increased field strength occurs because the domains inside the metal core temporarily align with the magnetic field produced by the currents flowing through the wire coils. The magnetic field from the ferrous core joins with the magnetic field created by the wire loops surrounding the core. This combination can be used to create very strong magnets that can be turned on or off instantly, called electromagnets. Electromagnets can be used to lift heavy objects such as automobiles or scrap metal. They are also used to support the weight of Mag-lev trains found in Europe and Asia. 8. Why does a compass needle move when it is placed next to an electrical circuit? Use information from the reading to support your response. _______________________________________________________________________ _______________________________________________________________________ Homework: Electromagnets Lab – Pre-reading and Hypothesis