Instructions
Read the short explanation about electromagnets below. Then, use what you have learned to complete the four activities that follow. Good luck!
What is an Electromagnet?
Have you ever wondered how a giant crane in a scrapyard can pick up a heavy car and then drop it? The secret is a powerful type of magnet that can be switched on and off: an electromagnet. Unlike the magnets on your refrigerator, which are permanent, an electromagnet is a temporary magnet.
It works because of a special relationship between electricity and magnetism. When an electric current (a flow of electrons) moves through a wire, it creates a small magnetic field around the wire. This field is usually too weak to notice. However, if you coil that wire many times around a piece of iron (like a nail or a bolt), called a core, you can concentrate that magnetic field and make it much, much stronger. The electricity flows from a power source (like a battery), through the coiled wire (the conductor), creating a powerful magnetic field in the iron core.
The best part? If you turn the electricity off, the magnetic field disappears. You can also make an electromagnet stronger by either increasing the amount of electric current or by adding more coils of wire around the core.
Activity 1: Label the Diagram
Imagine a simple electromagnet made from a battery, a copper wire, and an iron nail. The wire is wrapped around the nail, and the ends of the wire are connected to the battery. Use the words from the word bank to identify what each part represents.
Word Bank: Conductor (Wire), Core, Power Source, Magnetic Field
- The battery, which provides the electricity: ____________________
- The iron nail in the center of the coils: ____________________
- The copper wire that is coiled around the nail: ____________________
- The invisible area of magnetic force created around the device when it's on: ____________________
Activity 2: Fill in the Blanks
Complete the sentences below using the words from the box. Each word is used only once.
current stronger temporary magnetic field coils
An electromagnet is a ____________________ magnet that is created when an electric ____________________ flows through a wire. This flow creates a ____________________ around the wire. To make the effect more powerful, the wire is wrapped into many ____________________ around an iron core. Adding more turns to the wire or increasing the electricity will make the electromagnet ____________________.
Activity 3: True or False?
Read each statement carefully. Circle whether the statement is TRUE or FALSE.
- An electromagnet works even when the electricity is turned off.
TRUE / FALSE - You can make an electromagnet stronger by reducing the number of coils in the wire.
TRUE / FALSE - The iron core helps to focus the magnetic field.
TRUE / FALSE - Electromagnets are permanent magnets, just like the ones on a fridge.
TRUE / FALSE - A scrapyard crane uses an electromagnet to pick up and drop metal objects.
TRUE / FALSE
Activity 4: Real-World Application
Besides a scrapyard crane, think of another device that uses an electromagnet. Describe the device and explain why it is useful that its magnet can be turned on and off.
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Answer Key
Activity 1: Label the Diagram
- Power Source
- Core
- Conductor (Wire)
- Magnetic Field
Activity 2: Fill in the Blanks
An electromagnet is a temporary magnet that is created when an electric current flows through a wire. This flow creates a magnetic field around the wire. To make the effect more powerful, the wire is wrapped into many coils around an iron core. Adding more turns to the wire or increasing the electricity will make the electromagnet stronger.
Activity 3: True or False?
- FALSE
- FALSE
- TRUE
- FALSE
- TRUE
Activity 4: Real-World Application
(Answers will vary. Below are some possible examples. The student should identify a correct device and provide a logical explanation.)
- Example 1: Electric Bell. An electromagnet pulls a hammer to strike the bell. When it strikes, it breaks the circuit, turning the magnet off and letting the hammer fall back. This reconnects the circuit, and the process repeats, making the bell ring continuously. It's useful to turn it off so the hammer can reset.
- Example 2: Electric Motor. Electromagnets inside a motor are rapidly turned on and off to attract and repel permanent magnets, causing the motor to spin. If the electromagnets were always on, the motor wouldn't be able to turn continuously.
- Example 3: Loudspeaker. An electromagnet attached to a cone is rapidly turned on and off with varying strength, causing it to vibrate against a permanent magnet. These vibrations create the sound waves we hear. The ability to switch on/off and change strength is essential to creating different sounds.