What is a Temporary Magnet?

S4-SA1-0395

Grade Level:

Class 7

Space Technology, EVs, Climate Change, Biotechnology, HealthTech, Robotics, Chemistry, Physics

Definition

What is it?

A temporary magnet is a material that acts like a magnet only when it is near another magnet or when an electric current flows through it. Once the external magnetic field or electric current is removed, it loses its magnetism quickly.

Simple Example

Quick Example

Imagine you have a small iron nail. If you rub it against a strong bar magnet many times, the nail will become a temporary magnet and can pick up tiny paper clips for a short while. But soon, it will lose its ability to pick them up, just like your phone battery runs out of charge after some time.

Worked Example

Step-by-Step

Let's understand how an electromagnet works as a temporary magnet.
1. Take an iron nail and wrap a copper wire tightly around it many times.
2. Connect the two ends of the copper wire to a small battery (like the ones used in remote controls).
3. Observe: The iron nail will now attract small metal objects like paper clips or pins, acting like a magnet.
4. Disconnect the battery: As soon as you remove the battery, the electric current stops flowing through the wire.
5. Observe again: The iron nail immediately loses its magnetism and drops the metal objects it was holding.
ANSWER: The iron nail acted as a temporary magnet only when the electric current from the battery was flowing through the wire.

Why It Matters

Temporary magnets are crucial in many technologies we use daily, from lifting heavy scrap metal in recycling plants to making electric bells ring. Understanding them is key for future engineers in Robotics and for developing efficient motors in Electric Vehicles (EVs).

Common Mistakes

MISTAKE: Thinking temporary magnets are weak and not useful. | CORRECTION: Temporary magnets, especially electromagnets, can be made incredibly strong and are essential for controlled magnetic forces in many machines.

MISTAKE: Confusing temporary magnets with permanent magnets. | CORRECTION: Permanent magnets keep their magnetism all the time, like fridge magnets, while temporary magnets lose it quickly when the cause of magnetism is removed.

MISTAKE: Believing only iron can be a temporary magnet. | CORRECTION: While iron is common, other materials like nickel and cobalt, or alloys containing them, can also be used to make temporary magnets.

Practice Questions

Try It Yourself

QUESTION: What happens to a temporary magnet when the electric current supplying it is switched off? | ANSWER: It loses its magnetism.

QUESTION: Name one common material used to make the core of an electromagnet, which is a type of temporary magnet. | ANSWER: Iron (or soft iron).

QUESTION: A crane uses a large magnet to lift scrap metal. Is this likely a permanent or a temporary magnet? Explain why. | ANSWER: It's likely a temporary magnet (an electromagnet). This is because the crane needs to pick up the metal and then release it at another location, which can only be done by switching the magnetism on and off.

MCQ

Quick Quiz

Which of the following is a characteristic of a temporary magnet?

It always attracts magnetic materials.

It loses its magnetism when the magnetizing force is removed.

It is made of materials like steel.

It can only be found in nature.

The Correct Answer Is:

Option B correctly describes a temporary magnet's main feature: it loses magnetism when the external magnetic field or electric current is no longer present. Options A and C are more characteristic of permanent magnets or general magnetic properties, and option D is incorrect.

Real World Connection

In the Real World

You see temporary magnets in action every day! For example, the loud 'ding-dong' of your school's electric bell uses an electromagnet (a temporary magnet) to strike the bell. Also, the large cranes used in junkyards to lift and move heavy metal waste use powerful electromagnets that can be switched on and off to pick up and drop the metal.

Key Vocabulary

Key Terms

MAGNETISM: The force of attraction or repulsion between magnetic materials. | ELECTROMAGNET: A type of temporary magnet created by an electric current flowing through a coil of wire around a magnetic core. | MAGNETIC FIELD: The area around a magnet where its magnetic force can be felt. | SOFT IRON: A material often used for temporary magnet cores because it can be easily magnetized and demagnetized.

What's Next

What to Learn Next

Now that you understand temporary magnets, you're ready to explore 'Permanent Magnets.' You'll learn how they are different and why some materials keep their magnetism forever, building on your knowledge of magnetic properties.