Strength of Electromagnets

# Our Objective

To observe how the strength of an electromagnet depends upon the number of turns of the wire.

# The Theory

Magnets are substances that have the ability to draw in metallic materials like iron. The magnets can be temporary (such as electromagnets) or permanent magnets. The naturally occurring magnets are permanent magnets. A current carrying wire behaves like a magnet. When a compass is brought closer to the wire, the magnetic influence can be seen as a deflection of the needle. This magnetic effect of electric current can be used for making temporary magnets referred to as electromagnets. To maintain a magnetic field, an electromagnet needs a constant flow of electricity. Consequently, electricity may be utilised to switch the electromagnets on and off. An electromagnet usually consists of a long coil of insulated copper wire wound around an iron rod. When both ends of the coil are connected to a cell, a current flows through the coil. This generates a magnetic effect, magnetising the iron rod making it an electromagnet. The iron rod in this case is said to be the core of electromagnet. An electromagnet attracts magnetic objects (such as pins, clips, and other objects made of iron, steel, etc.) similar to real magnets when they are brought close to it.

## Strength of Electromagnets

The strength of electromagnets depends on several factors such as: Strength of current passing through the coil: As the current flowing through the coil increases, strength of electromagnet increases. We can increase the current by adding more cells in the circuit.

• Number of turns in the coil: The strength of electromagnets rises with the number of coils. The magnetic fields help each other and become stronger if the loops curl in the same direction. The fields cancel each other out if it curls in the opposite directions.
• Core of electromagnet: If the wire is wound on a material that is easier to magnetize such as iron, then the overall strength of the magnetic field increases.
• Thickness of the core: A thicker core might make a more powerful magnet and attract a significant number of nails.
• Thickness of the wire: A slight change is observed on changing thickness of the wire with thicker wire attracting more nails.

In fact, electromagnets are the strongest magnets made.

An electromagnet's magnetism can be activated or deactivated as required. With a permanent magnet, this is impossible. We can increase the strength of an electromagnet by either increasing the number of turns in the coil or the current that flows through it.

## Electromagnet applications

• Electromagnets vary in strength from very weak but sensitive electromagnets used to detect other magnets or electric currents to the huge research instruments.
• Their wide range of application varies from the MRI machines used in hospitals to remote-control toy cars.
• Electromagnets are used in the construction of a large number of devices like electric bells, loudspeakers, electric motors, electric fans, toys and telephone instruments, etc.
• Strong electromagnets fitted on cranes are used to lift heavy iron and steel objects.
• They are also used to separate magnetic materials like iron from other metal scrap or junk for recycling.

# Learning Outcomes

1. Students learn that electric current can produce magnetic effects.
2. Students learn to make their own electromagnets.
3. They learn properties of electromagnets and how its strength is affected.