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AQA GCSE Physics > Magnetism > Flashcards

Flashcards in Magnetism Deck (56)
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What materials can be made into permanent magnets?



What elements are ferromagnetic?

Iron, nickel and cobalt


What causes ferromagnetism?

Domains (mini-magnets) that exist as part of the metal's structure aligning


What causes the alignments of the domains?

heating, working or applying an existing magnetic field


What is a magentic field?

A region surrounding a magnet in which another magnet or ferromagnetic material will experience a magnetic force


Which way do arrows point in a field pattern?

North to south


How can field patterns be plotted?

- with a plotting compass
- place it in area around magnet and the needle will line up along the field lines
- head is a north pole so points towards a south pole


How do we know that the earth has a magnetic field?

Magnets suspended above the earth experience a force


How does the north pole of a compass point to geographic north?

- north pole is attracted to and thus points at magnetic south pole
- Earth's magnetic south pole is the geographic north pole


What causes earth's magnetic field?

The liquid nickel-iron outer core of the earth


Why does the solid iron core of the earth not exhibit magnetic properties?

it is at too high a temperature


How does induced magnetism take place?

- When a magnetic material is in close proximity to, or in contact with, a permanent magnet
- permanent magnet's pole causes the opposte pole of the domains in the ferromagnetic material to attract to it and align.


Why is induced magnetism only temporary?

When the permanent magnet is removed, the domains fall back into random arrangement


Why does induced magnetism always result in attraction?

Since the induced magnet always has the opposite pole closest to the permanent magnet


other than magnets, what else can produce magnetic fields?

An electric current


What does the magnetic field in a current carrying wire look like?

Increasingly sized circles flowing the direction as shown by the right hand rule


What is a solenoid?

A current carrying coil


What determines the polarity of the filed in a solenoid?

The direction of current round the circuit


How do solenoids become electromagnets?

With the inclusion of a soft iron core


What is a soft iron core?

A pure iron core which isn't alloyed


How can electromagnets be switched on and off?

- domains in the iron core align to form a temporary, induced magnet when current flows through the coil
- when the current is switched off, alignement of domains is lost so no magnetic effect


Why cant steel cores be used in electromagnets?

Sicne steel cores would become permanently magnetised even when the current is turned off


What does the interaction of magnetic fields result in?

A force being exerted


What is the relationship between F and I? What variables are kept constant?

Directly proportional - the length of the current carrying wire in the magnetic field and the magnetic field strength of the magnets


Whaat equation gives the magnitude of the force on a current carrying wire in a magnetic field?



What is 1 tesla exactly equal to?

1 N/Am


What does each finger represent in fleming's left hand motor role?

thumb - force
first finger - magnetic field (north to south)
second finger - current direction


What symbols represent a force into the plance and out of the plane?

A circle with a cross shows a force into the plane whereas a circle with a dot shows a force out of the plane


Why does current need to keep flowing the same way round a motor?

To keep the motor spinning rather than turning back and forth


What enables current to flow the same way round the coil in a motor? What does this mean?

A split ring communtator. Means the force on each side of the coil is kept in the same direction to maintain the rotation of the coil