Section 6 - Electric and Magnetic Fields Flashcards
(40 cards)
What causes a build-up of static?
Friction between two insulators.
What is the rule for the interactions between charges?
Opposite charges attract, like ones repel.
How do electrically charged objects attract uncharged objects? What is it called?
The charged object’s charges repel or attract the electrons on the surface of the other object, this creates a charged surface that is attracted to. This is known as attraction by induction.
What are sparks? What causes them?
A large enough potential difference between an object and the earth. The spark is the electrons jumping from the object to the earth.
What are common uses of static electricity?
Photocopiers, paint and insecticide sprayers, industrial chimney protection.
What are the dangers of static electricity?
Static can build up when refueling and cause an explosion.
Static can build up in an airplane and disrupt communications.
Lightning.
How can electrostatic charge build-up be prevented and dissipated?
By earthing the object.
What is an electric field?
The region around a charged object where, if a second charged object were to be placed inside, a force on both of the charged objects would exerted.
What happens to electric field strength as you get closer to the object creating it?
It increases.
How do electric fields explain sparking?
Statically charged objects create their own electric field, sparks are caused by a high enough potential difference that causes electrons to be removed from air particles, causing ionisation. ionized particles are often highly conductive and so current flows, this is the spark.
What is a magnetic field?
The region around a magnet where, if another magnet or magnetic material were to be placed inside, a force would be placed on all the objects in the field, provided they were magnetic or magnets.
What is the rule between magnetic poles and their interactions with one another?
Like poles will repel one another where opposite poles attract.
How do compasses work?
The compass contains a tiny, free spinning bar magnet, it will always line up with whatever magnetic field it is in, this is most often Earth’s.
What does the fact that the Earth produces its own magnetic field show about the earth’s core?
That its core must be magnetic.
What are the three magnetic metal elements?
Iron, nickel and copper.
What must the magnetic force between a magnet and a magnetic material always be?
Attractive.
What are the two types of magnet?
Permanent and induced.
What types of magnetic material are there? What differentiates them?
Soft and hard, magnetically soft materials demagnetise very quickly and easily where magnetically hard materials are harder and take longer times to demagnetise.
What are some common uses of magnetic materials?
Fridge doors, cranes, doorbells, magnetic separators, maglev trains, MRI machines, speakers and microphones.
What happens when a current flows through a long, straight conductor?
A magnetic field is created around it, as a series of concentric rotating circles.
What happens to the magnetic field around a current carrying wire the closer you get, or the larger the current through the wire?
The field becomes stronger.
What technique can be used to find the direction of a field around a current carrying wire?
The right-hand thumb rule.
What is the motor effect?
Where a current carrying wire is put between magnetic poles, the magnets exert a force on the wire.
Describe the equation for the force acting on a conductor in a magnetic field.
F=B×I×l
F = Force B = Magnetic flux density I = Current l = Length
