Definition / Example
Ni, Co, Fe, Steel – material which produces an attractive or repulsive force in a region of space around it.
Shows the direction of a magnetic field & field lines.
Magnetic Field Line
A closed directional loop which shows a region of space with a field.
Closeness of Field Lines
This is the way we show the strength of a magnetic field.
Area of a substance which results in a “net force” acting. In a magnet the domains are “aligned”
This is a complex compound which produces a strong magnetic field for the size of magnet
This is the way we talk about the direction of a magnetic field. N -> S (Birds fly south in the winter!)
Coil of wire in which when an electrical current passes produces a temporary magnetic field. Used to create physical motion.
Usually a solenoid with a metal bar inserted with can be magnetised by the field. This reinforces the field.
The use of an electromagnet to move a metal switch to turn on another circuit.
Use this PowerPoint for the lesson topics…. 02 Magnetism
Lesson 1/2 Magnetic Features and Domains & Fields and Lines (Plus Northern Lights)
A long time ago the Ancient Greeks discovered a rock which they called lodestone. Pieces of this rock sometimes attracted each other. Sometimes they pushed each other away, or repelled.
- A magnet settles in a North–South direction when hung by a thread.
- It has a pole near each end – North-seeking and South-seeking.
Magnets attract magnetic materials. Iron, steel, nickel and cobalt are magnetic materials. Magnetic materials are not attracted to each other but they can be made into magnets.
- Iron is easy to magnetise but loses its magnetism easily.
- Steel is hard to magnetise but keeps its magnetism.
Wider reading…William Gilbert (1544 – 1603)
Gilbert was an English physician and scientist, the first man to research the properties of the lodestone (magnetic iron ore), publishing his findings in the influential ‘De Magnete’ (‘The Magnet’). He also invented the term ‘electricity‘.
William Gilbert (also Gilberd) was born on 24 May 1544 into a prosperous family in Colchester, Essex. He was educated at Cambridge University, where he received a BA, MA and MD, after which he became a senior fellow. He practised as a doctor in London for many years and in 1600 became president of the Royal College of Physicians.
‘De Magnete’ was published in 1600 and was quickly accepted as the standard work on electrical and magnetic phenomena throughout Europe. In it, Gilbert distinguished between magnetism and static (known as the amber effect). He also compared the magnet’s polarity to the polarity of the Earth, and developed an entire magnetic philosophy on this analogy.
Gilbert’s findings suggested that magnetism was the soul of the Earth, and that a perfectly spherical lodestone, when aligned with the Earth’s poles, would spin on its axis, just as the Earth spins on its axis over a period of 24 hours.
Gilbert was in fact debunking the traditional cosmologists’ belief that the Earth was fixed at the centre of the universe, and he provided food for thought for Galileo, who eventually came up with the proposition that the Earth revolves around the Sun. Gilbert died on 30 November 1602, probably of the plague.
Lesson 3 Making an Electromagnet
When an electric current passes through a coil of wire, called a solenoid, it creates a magnetic field around it. The solenoid behaves like a magnet.
If an iron rod is put inside the solenoid the iron rod becomes magnetised. The iron rod is called an iron core. The core makes the magnetic field stronger. The solenoid and core together make an electromagnet.
A stronger electromagnet has a greater magnetic attraction so can hold a bigger load. You can increase the strength of an electromagnet by:
- 1.increasing the size of the current.
- 2.winding more turns on the solenoid.
- 3.Changing the core material: Fe, wood, Al
There is a limit to the strength of an electromagnet due to the Physical features.
Lesson 4 Electromagnet Uses
You should know how these things work…
- alarm bell
- relay switches
Lesson 5 Solenoids and Uses
A solenoid is described as a coil of wire usually wrapped around a metal core.
When the solenoid receives an electric current, it creates a magnetic field that can become useful in controlling locks, water pressure, air pressure, clamps or similar.
It can be used in a simple locking device, medical clamping equipment, an automotive gear box, and an air conditioning unit.
In industrial circles, it is often the term used to refer to solenoid valves, which is a device designed to actuate hydraulic or pneumatic valves.