Magnets & Magnetic Fields (OCR GCSE Physics A (Gateway)): Flashcards
Exam code: J249
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Define the law of magnetism.
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Cards in this collection (40)
Define the law of magnetism.
The law of magnetism states that like poles repel and unlike poles attract.
True or False?
Two north poles held close together will attract each other.
False.
Two like poles repel each other. Only unlike (opposite) poles attract.
Identify the type of force involved in magnetic attraction and repulsion.
Magnetic attraction and repulsion are examples of a non-contact force — the magnets do not need to touch.
Two unlike poles will .......... each other, while two like poles will .......... each other.
Two unlike poles will attract each other, while two like poles will repel each other.
how do magnetic field lines between two repelling magnets differ from those between two attracting magnets?
Between repelling magnets, field lines curve away from each other and do not connect. Between attracting magnets, field lines run from the north pole of one magnet to the south pole of the other.
Name the two poles of a magnet.
Magnets have two poles: a north pole and a south pole.
True or False?
Magnets must be in contact with each other for an attractive force to act between them.
False.
Magnetic attraction and repulsion are non-contact forces — they act without the objects touching.
explain how you would test whether an object is a magnet or just a magnetic material
Bring the object close to a known magnet. If it can be repelled by either pole, it is a magnet. If it is only ever attracted and never repelled, it is a magnetic material.
Define a permanent magnet.
A permanent magnet produces its own magnetic field and does not lose its magnetism.
The magnetic metals in the Periodic Table include iron, .......... and nickel. Steel is also magnetic because it contains ...........
The magnetic metals in the Periodic Table include iron, cobalt and nickel. Steel is also magnetic because it contains iron.
True or False?
An induced magnet keeps its magnetism after it is removed from a magnetic field.
False.
An induced magnet loses most or all of its magnetism quickly once it is removed from the magnetic field.
Define an induced magnet.
An induced magnet is a magnetic material that becomes temporarily magnetised when placed inside a magnetic field.
when a magnetic material is placed near a north pole, what pole forms at the end closest to the magnet?
A south pole forms at the end closest to the magnet. The induced pole is always opposite to the nearby pole so that the material is attracted to the magnet.
True or False?
Aluminium is a magnetic material and will be attracted to a magnet.
False.
Aluminium is a non-magnetic material and is unaffected by a magnetic field.
a metal rod is held near a bar magnet and is attracted to it. does this prove the rod is a magnet?
No. Both magnets and magnetic materials are attracted to a magnet. To confirm the rod is a magnet, it must also be able to be repelled by either pole.
List four magnetic materials.
The magnetic materials are iron, cobalt, nickel, and steel.
Define a magnetic field.
A magnetic field is the region around a magnet where a force acts on another magnet or on a magnetic material.
True or False?
Magnetic field lines point from the south pole to the north pole of a magnet.
False.
Magnetic field lines always point from the north pole to the south pole.
Explain what the spacing of magnetic field lines shows about field strength.
Close field lines indicate a strong magnetic field; field lines that are far apart indicate a weak magnetic field.
A uniform magnetic field has the same .......... and .......... at all points. It is produced between two .......... poles.
A uniform magnetic field has the same strength and direction at all points. It is produced between two opposite poles.
describe how a plotting compass is used to map the magnetic field around a magnet
Place the compass next to the magnet, mark a dot where the north end of the needle points, then move the compass to that dot and repeat. Join the chain of dots with a smooth curve to form a field line, and add an arrow showing direction from north to south.
True or False?
The magnetic field of a bar magnet is strongest at its poles.
True.
The field lines are closest together at the poles, indicating the field is strongest there.
state two rules that must be followed when drawing magnetic field lines
Field lines must never touch or cross each other. They must have arrows showing direction from the north pole to the south pole.
Describe the appearance of a uniform magnetic field between two opposite poles.
In a uniform field, the field lines are equally spaced and parallel, with arrows all pointing in the same direction from north to south.
State what produces the Earth's magnetic field.
The core of the Earth is magnetic and produces the Earth's own magnetic field.
True or False?
The geographic North Pole acts as a magnetic north pole.
False.
The geographic North Pole acts as a magnetic south pole. That is why the north pole of a compass needle is attracted towards it.
explain why a magnetic compass needle points towards the geographic North Pole
The geographic North Pole is a magnetic south pole. The north pole of the compass needle is attracted to it because unlike poles attract.
The Earth's magnetic field is similar to that of a .........., with the geographic North Pole acting as a magnetic .......... pole.
The Earth's magnetic field is similar to that of a bar magnet, with the geographic North Pole acting as a magnetic south pole.
True or False?
In the absence of any other magnets, a compass needle will point towards the geographic North Pole.
True.
The Earth's own magnetic field causes the compass needle to point north in the absence of other magnetic materials.
what type of magnetic pole is the geographic South Pole, and how does a compass respond to it?
The geographic South Pole is a magnetic north pole. The north pole of a compass needle is repelled from it.
State the evidence that the Earth's core is magnetic.
A magnetic compass always points north in the absence of other magnets, which shows the Earth's core generates its own magnetic field.
Describe the shape of the magnetic field around a current-carrying wire.
The magnetic field around a current-carrying wire forms concentric circles centred on the wire.
True or False?
A magnetic field exists around a wire even when no current is flowing through it.
False.
A magnetic field is only produced around a wire when a current is flowing. No current means no magnetic field.
describe how to use the right-hand thumb rule for a current-carrying wire
Point the thumb of the right hand in the direction of the current. The curled fingers show the direction of the magnetic field around the wire.
The strength of the magnetic field around a wire increases with a .......... current and decreases with greater .......... from the wire.
The strength of the magnetic field around a wire increases with a larger current and decreases with greater distance from the wire.
State what the magnetic field around a solenoid resembles.
The magnetic field around a solenoid is similar to that of a bar magnet, with a north pole at one end and a south pole at the other.
True or False?
When viewed from one end of a solenoid, a clockwise current indicates a south pole at that end.
True.
A clockwise current at one end of a solenoid indicates a south pole at that end. An anticlockwise current indicates a north pole.
state three ways to increase the strength of the magnetic field around a solenoid
The field strength can be increased by:
increasing the current
increasing the number of coils
adding an iron core through the centre of the coils.
explain why adding an iron core to a solenoid increases the strength of its magnetic field
The iron core becomes an induced magnet when current flows through the coils. Its magnetic field combines with the solenoid's field to produce a much stronger overall magnet.
Reversing the direction of .......... flowing through a wire will reverse the .......... of the magnetic field around it.
Reversing the direction of current flowing through a wire will reverse the direction of the magnetic field around it.
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