Year 8 Science: Magnetism and Lab Safety

Year 8 Science - Electricity and Magnetism: Magnetism

• The following lessons will cover Magnetism, Magnetic Fields, Electromagnets, and Using Electromagnets

Laboratory Safety Rules

• Follow all rules to ensure the safety of yourself and peers
• Always use equipment properly and safely
• Follow all safety instructions from teachers and other staff
• Only work in the lab when a teacher is present
• Wear safety goggles when doing practical work with chemicals
• Clean all spills immediately and check with the teacher for special instructions
• Tie long hair back and remove any dangling jewelry
• Never put anything in or near your lips or mouth in the lab
• Wash chemicals off your skin straight away
• Do not mess around in the lab
• Never point a test tube at anyone
• Never put chemicals down the sink unless the teacher says ok
• Do not leave bags or coats lying around the floor

Overview & Big Ideas

• Electricity is a crucial energy store in daily life
• Concepts about electricity, conductors, insulators, and circuits are developed by:
  • Understanding how electrical current is measured
  • How energy is transferred in a circuit
  • Examination of magnetism
  • Link between electricity and magnetism using electromagnets
• The concept of modeling and models is used to explain phenomena that aren't directly observable

Challenge Questions

• What is electric current and how can it be measured?
• What is potential difference and how can it be measured?
• What are series and parallel circuits and how are they different?

Lesson 7: Magnets

• Aim: Describe how magnets interact, understand what materials are magnetic, and describe Earth's magnetic field and its uses

The Mystery of Magnetism

• The term "magnet" originates from a Greek shepherd named Magnes
• It's believed people in China were the first to use a magnetic compass
• In Britain, magnets were called "lodestones," meaning "leadstones"
• Travellers used lodestones to navigate unknown places and prevent getting lost
• Though magnets are better understood today, aspects of their function remain mysterious

Magnetic Elements

• For a substance to be magnetic (attracted to a magnet), it MUST contain one of the three magnetic elements:
  • Iron (Fe)
  • Nickel (Ni)
  • Cobalt (Co)

Magnetic Poles

• Every magnet has two poles:
  • A north-seeking-pole
  • A south-seeking-pole
• Like poles repel and opposite poles attract

Lesson 8: Magnetic Fields

• Aim: Describe the shape of magnetic fields of a bar magnet and between like poles and unlike poles.

Magnetic Force

• Magnetism is a non-contact force
• Objects experience a magnetic force without touching the magnet
• A magnetic field of force extends beyond the magnet
• This field is called the MAGNETIC FIELD

Magnetic Field Properties

• Every magnet has a magnetic field that fills the space around it
• A magnetic field's strength is greatest at the poles
• The magnetic field strength is indicated by how close the lines are to one another
• Field lines farther from the magnet indicate a weaker magnetic field
• The magnetic field lines curve around from the north pole to the south pole of the magnet
• Different types of magnets have different magnetic fields, but all have a north-seeking-pole and a south-seeking-pole

Earth's Magnetic Field

• Earth has a magnetic field that looks like the magnetic field of a bar magnet
• The Earth's magnetic field is thought to be caused by electric currents in the liquid outer core
• This magnetic field protects the planet from harmful solar wind and cosmic radiation
• A compass is an instrument that uses a magnetic needle to align with Earth's magnetic field, indicating the direction of north

Lesson 9: Electromagnets

• An electric current flowing in a wire creates a magnetic field around the wire and the field lines are circles
• A looped wire with a current creates straight magnetic field lines at the loop's center
• A coil made of many loops is termed a solenoid
• Shaping the magnetic field of a solenoid looks like one around a bar magnet
• Electromagnets can be turned on and off with a switch
• Magnetic material, like iron, in the centre of the coil is called a core, this makes the electromagnet stronger

Electromagnet Strength

• Strength of an electromagnet depends on:
  • Number of turns/loops on the coil of wire
  • Current flowing through the wire
  • Type of core used

Lesson 10: Using Electromagnets

• Electromagnets have a variety of useful features because they can: be turned on/off, vibrate, and alter the current flowing through them for strong strength

Electric Bell

• When the switch is pushed, the circuit completes and a current flows
• The magnetic field is produced around the electromagnet
• The iron armature is attracted to the electromagnet, and strikes the bell
• The circuit breaks and stops moving, and the coil and core are no longer magnetized
• The iron armature then moves back to original position
• The process repeats itself, and the bell rings a second time

Circuit Breaker Function

• Circuit breakers are safety devices to prevent large currents
• A current flowing in the wire makes the electromagnet strong enough to attract the iron catch
• The catch moves, breaking the circuit
• To turn back on, the reset button needs to be pushed

Earphones

• Contain loudspeakers
• Current flows from a device into a coil of wire inside the earphone
• The coil becomes an electromagnet
• A magnet inside the earphone repels and attracts the electromagnet
• This makes the cone move back and forth, producing sound

Electromagnets vs Permanent Magnets

• Key differences between the two
  • Electromagnets can be turned off
  • The strength of electromagnets can be varied
• Electromagnets can be made much stronger than permanent magnets
• Electromagnet applications: electric doorbells, levitating trains, moving cars in a scrapyard and MRI scanners