physica topic D : Fields

Gravitational field

A region of space where a test mass experiences a gravitational force due to another mass

Gravitational field strength

The gravitational force experienced per unit mass at a point in a gravitational field

Newton's law of universal gravitation

The gravitational force between two point masses is proportional to the product of their masses and inversely proportional to the square of the distance between them

Point mass

An object whose dimensions are negligible compared with the distances involved

Gravitational field line

An imaginary line whose tangent gives the direction of the gravitational force on a test mass

Radial gravitational field

A gravitational field whose field lines point towards a central mass

Uniform gravitational field

A gravitational field with constant strength and direction

Inverse square law

A relationship in which a quantity is inversely proportional to the square of the distance from its source

Kepler's first law

A planet moves in an elliptical orbit with the Sun at one focus

Kepler's second law

A line joining a planet to the Sun sweeps out equal areas in equal time intervals

Kepler's third law

The square of the orbital period is proportional to the cube of the semi major axis for bodies orbiting the same central mass

Orbital speed

The speed of an object moving along its orbit

Orbital period

The time taken for an object to complete one orbit

Centripetal force

The resultant force directed towards the centre of a circular path

Centripetal acceleration

The acceleration directed towards the centre of a circular path

Geostationary satellite

A satellite in a circular equatorial orbit moving in the same direction as Earth's rotation with a period equal to Earth's rotational period so it remains above the same point on Earth

Electric charge

A property of matter that causes objects to experience electric forces

Conservation of electric charge

The total electric charge in an isolated system remains constant

Conductor

A material containing mobile electric charges that can move through it

Insulator

A material in which electric charges cannot move freely

Electric field

A region of space where an electric charge experiences an electric force

Electric field strength

The electric force experienced per unit positive test charge at a point

Electric field line

An imaginary line whose tangent gives the direction of the force on a positive test charge

Uniform electric field

An electric field with constant strength and direction

Radial electric field

An electric field whose field lines point towards or away from a central charge

Coulomb's law

The electrostatic force between two point charges is proportional to the product of their charges and inversely proportional to the square of their separation

Electric potential difference

The work done or energy transferred per unit charge between two points

Electric current

The rate of flow of electric charge

Conventional current

The direction in which positive electric charges would flow

Electron drift speed

The average velocity of free electrons through a conductor due to an applied electric field

Magnetic field

A region of space where a moving charge or current carrying conductor can experience a magnetic force

Magnetic field line

An imaginary line whose tangent gives the direction indicated by the north pole of a compass

Magnetic flux density

The magnetic force per unit current per unit length on a straight conductor perpendicular to the magnetic field

Tesla

The magnetic flux density that produces a force of one newton on a one metre wire carrying one ampere perpendicular to the magnetic field

Solenoid

A coil of wire that produces a magnetic field when an electric current flows through it

Right hand grip rule

A rule where the thumb points in the direction of conventional current and the curled fingers indicate the direction of the magnetic field

Fleming's left hand rule

A rule where the first finger indicates the magnetic field and the second finger indicates conventional current while the thumb indicates the direction of force

Magnetic force on a current carrying conductor

The force experienced by a conductor carrying electric current in a magnetic field

Magnetic force on a moving charge

The force on a moving charged particle that acts perpendicular to both its velocity and the magnetic field

Circular motion in a magnetic field

The motion of a charged particle in a circular path when its velocity is perpendicular to a uniform magnetic field

Helical motion in a magnetic field

The spiral motion of a charged particle whose velocity has components both parallel and perpendicular to a magnetic field

Hall effect

The production of a potential difference across a current carrying conductor due to the separation of moving charges by a perpendicular magnetic field

Hall voltage

The potential difference produced across a conductor due to the Hall effect