Review Flashcards on Force Fields and Electromagnetism

Flashcards covering key vocabulary and concepts from the lecture notes on force fields, gravity, electric fields, capacitance, magnetic fields, and electromagnetism.

Force Field

An area in which an object experiences a non-contact force.

Gravitational Field

A force field formed during the interaction of masses.

Electric Field

A force field formed during the interaction of charges.

Newton’s Law of Gravitation

The magnitude of the gravitational force between two masses is directly proportional to the product of the masses, and inversely proportional to the square of the distance between them.

Gravitational Field Strength (g)

The force per unit mass exerted by a gravitational field on an object.

Uniform Field

Exerts the same gravitational force on a mass everywhere in the field, as shown by the parallel and equally spaced field lines.

Radial Field

The force exerted depends on the position of the object in the field, e.g as an object moves further away from the centre, the magnitude of the force would decrease because the distance between the field lines increases.

Gravitational Potential (V)

The work done per unit mass against gravitational force to move an object from infinity to a given point.

Gravitational Potential Difference (ΔV)

The energy needed to move a unit mass between two points.

Equipotential Surface

Surfaces which are created through joining points of equal potential together, therefore the potential on an equipotential surface is constant everywhere.

Kepler’s Third Law

The square of the orbital period (T) is directly proportional to the cube of the radius (r): T^2 ∝ r^3

Escape Velocity

The minimum velocity an object must travel at in order to escape the gravitational field at the surface of a mass.

Synchronous orbit

A synchronous orbit is one where the orbital period of the satellite is equal to the rotational period of the object that it is orbiting

Geostationary Satellites

Follow a specific geosynchronous orbit, meaning their orbital period is 24 hours and they always stay above the same point on the Earth, because they orbit directly above the equator.

Low-orbit Satellites

Have significantly lower orbits in comparison to geostationary satellites, therefore they travel much faster meaning their orbital periods are much smaller.

Coulomb’s Law

The magnitude of the force between two point charges in a vacuum is directly proportional to the product of their charges, and inversely proportional to the square of the distance between the charges.

Electric Field Strength (E)

The force per unit charge experienced by an object in an electric field.

Absolute Electric Potential (V)

The potential energy per unit charge of a positive point charge at that point in the field.

Electric Potential Difference (ΔV)

The energy needed to move a unit charge between two points.

Capacitance (C)

The charge stored (Q) by a capacitor per unit potential difference (V).

Dielectric

An insulating material between the plates of a capacitor.

Permittivity (ε)

A measure of the ability to store an electric field in the material.

Relative Permittivity (εr)

Also known as the dielectric constant of a dielectric, which is used to calculate the capacitance of a capacitor.

Time Constant

The product of resistance and capacitance (RC).

Time to Halve (T1/2)

The time taken for the current, charge or potential difference of a capacitor to discharge to half of the initial value.

Magnetic Flux Density (B)

Measure of the strength of the magnetic field and it is measured in the unit Tesla.

Fleming’s Left Hand Rule

ThuMb - represents the direction of the Motion/force, First finger - represents the direction of the Field, SeCond finger - represents the direction of the Conventional Current.

Cyclotron

An application of the circular deflection of charged particles in a magnetic field is a type of particle accelerator.

Magnetic Flux (Φ)

A value which describes the magnetic field or magnetic field lines passing through a given area, and it is calculated by finding the product of magnetic flux density (B) and the given area (A), when the field is perpendicular to the area.

Magnetic Flux Linkage (Nϕ)

The magnetic flux multiplied by the number of turns N, of a coil.

Electromagnetic Induction

When a conducting rod moves relative to a magnetic field, the electrons in the rod will experience a force (as they are charged particles), and build up on one side of the rod, causing an emf to be induced in the rod.

Faraday’s Law

The magnitude of induced emf is equal to the rate of change of flux linkage.

Lenz’s Law

The direction of induced current is such as to oppose the motion causing it.

Alternating current

When a coil rotates in a magnetic field an emf is induced and will change direction with time.

Transformer

Used with alternating currents to change the size of their voltage.

Step-up transformer

Increases the input voltage by having more turns on the secondary coil than the primary.

Step-down transformer

Decreases the input voltage by having less turns on the secondary coil than the primary.

Eddy Currents

Induced by the alternating magnetic field in the primary coil, and form a loop.

Laminated iron core

The core is made using layers of iron between layers of an insulator, because the eddy currents cannot pass through the insulator and so their amplitude is reduced.