Electromagnetism Flashcards

Flashcards about Electromagnetism

What is created by electric current?

Electric current creates a magnetic field.

What is created by a changing magnetic field?

Electric current.

What four laws encompass all of electromagnetism?

Gauss' Law, No Magnetic Charge, Ampere's Law, and Faraday's Law.

What does magnetostatics study?

The spatial distribution of magnetic fields in the vicinity of permanent magnets and stationary currents and the force exerted by a magnetic field on magnets and currents.

What is a magnetic field?

A region of space surrounding a magnet or a current-carrying conductor in which a force is experienced by another magnet or current-carrying conductor or any magnetic material.

What is the first property of magnetic lines of force?

Lines of force never intersect or cross.

What is the second property of magnetic lines of force?

Points out of a North pole and into a south pole.

What is the third property of magnetic lines of force?

A line (curve) such that tangent to it at any point is the direction of the field at this point.

What is the fourth property of magnetic lines of force?

Magnetic field lines always form closed loops.

What is a magnet?

Metallic object that has the property of attracting certain other metallic objects.

What is the definition of magnetic material?

Substances that can be attracted by a magnet are said to be magnetic e.g. Iron, steel, nickel & cobalt. Non-magnetic materials include plastic, wood, brass, glass, air, aluminium & copper.

What is magnetism?

The ability of a magnet to attract magnetic substances.

What is a permanent magnet?

Do not depend on electrical energy to keep its magnetic properties. Usually made of steel which is difficult to magnetise but does not lose its magnetism easily.

What is an electromagnet?

Are temporary magnets made by passing electric current through a coil of wire. Usually made of iron.

How can we make an electromagnet stronger? (i)

Wrapping the coil around an iron core.

How can we make an electromagnet stronger? (ii)

Adding more turns to the coil.

How can we make an electromagnet stronger? (iii)

Increasing the current flowing through the coil.

What are the useful properties of an electromagnet?

It can be switched on/off, the strength can be controlled, it can be made very strong.

What are poles?

We name the ends of a magnet “the poles”. (North and & South). More correctly they should be referred to as the “North seeking pole” and “South seeking pole”.

What is the S.I. Unit of magnetic flux?

Weber (Wb).

What is the S.I. Unit of magnetic flux density B?

Tesla (T) defined as the force per unit length, per unit current (N/m/A) (1T = 1Wb/m2).

What is the second property of magnets?

Magnets align themselves with magnetic field (force) just like electric dipoles in electric field.

What is the third property of magnets?

Freely rotating (suspended) magnets rests in a earth’s magnetic N-S direction. (The earth acts like a huge magnet with its magnetic south pole near the geographic north pole).

What is the fourth property of magnets?

Magnets have magnetic fields around them.

What do similar poles do?

Like poles repel each other & Unlike poles attract each other.

What is the sure test for the polarity of a magnet?

Repulsion is the sure test for the polarity of a magnet because a pole repels a like pole but attracts both an unlike pole and an unmagnetised magnetic material.

What magnetic pole is near the geographic North pole?

The geographic North pole has a South magnetic pole associated with it (Since a north seeking pole of a magnet will point towards it).

What are methods of making a magnet?

Electrical, heating, single touch and divided touch.

What are methods of demagnetizing a magnet?

Electrical, heating, rough treatment.

How does each domain behave?

Each domains behaves like a tiny magnet with a north and south pole.

What concept is crucial to understanding magnetic materials?

The average magnetic field produced by many magnetic dipoles which are all aligned.

What did Hans Christian Oersted discover?

A magnetic compass is deflected around a current-carrying conductor.

What did Michael Faraday discover?

A changing magnetic field induces an electric current in a conductor.

What rules can be used to establish the direction of magnetic field produced by wires carrying electric current?

Maxwell's corkscrew rule or Right-hand grip rule.

What are the rules of attraction between currents?

Like currents attract, unlike currents repel

In a coil, what is the rule to determine the direction of the magnetic field?

Looking into the coil: North Anticlockwise, South clockwise.

Where are the applications of magnetic fields or electromagnets?

Loudspeakers, Video and audio cassettes, Electromagnets: electric bell, relay, telephone, circuit breakers, Motor armature: blender, fans, Transformer core (temporary), Electromagnets in lifting and transporting heavy pieces of iron and steel (crane), Separation of mixtures.

What is shielding in electromagnetism?

The soft iron ring screens a piece of equipment from a magnetic field as it carries the field lines around the equipment. Thus protecting equipment that are sensitive to stray magnetic fields.

Why are metal keepers placed across the ends of bar magnets for storage?

The keepers help to keep the magnets magnetised. The material used for the keepers becomes strongly magnetised when placed in contact with the magnets, but does not remain magnetised when taken away from the magnets.