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Physics Definitions > Fields And Their Consequences > Flashcards

Fields And Their Consequences Flashcards

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1
Q

What is back EMF?

A

An emf generated by the coil in an AC generator that acts against the potential difference that has been supplied to the motor.

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2
Q

What is capacitance?

A

The charge stored per unit pd in a capacitor?

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3
Q

What is a capacitor?

A

An electrical component that stores charge. A parallel-plate capacitor is made of two parallel conducting plates with an insulator between them (dielectric).

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4
Q

What is Coulomb’s Law?

A

The size of the forced that acts between two point changes is proportional to the product of their charges and inversely proportional to the square of their separation. It is attractive for opposite charges and repulsive for like charges.

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5
Q

What is a cyclotron?

A

A particle accelerator made up of two D shaped electrodes positioned opposite each other. The electric field changes direction each time a particle moves from one electrode to the other, causing the particle to accelerate.

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6
Q

What does dielectric mean?

A

An insulating material placed between the two plates of a capacitor in order to increase the amount of charge it can store.

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7
Q

What is an electrical conductor?

A

A material that contains freer electrons that are able to move throughout the material and carry charge.

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8
Q

What is an electrical insulator?

A

A material that does not contain any free electrons. All electrons in an insulator are part of the individual atoms that make it up.

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9
Q

What is an electric field?

A

A region surrounding a charged object which causes a force to be exerted on any charged object placed within the field.

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10
Q

What is electric field strength?

A

The force per unit positive charge exerted on a charged object p;aced at that point in the field. This is a vector acting in the same direction as the force on a positive charge.

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11
Q

What is electric potential?

A

The work done per unit charge on a positive test charge in bringing it from infinity to that point in the field.

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12
Q

What is electromagnetic induction?

A

When an emf is induces in a wire/conducting rod when it is moved relative to the magnetic field.

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13
Q

What is equipotential?

A

A surface of constant potential. No work is done by the field when an object moves along an equipotential.

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14
Q

What is escape velocity?

A

A surface of constant potential. No work is done by the field when an object moves along an equipotential.

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15
Q

What is escape velocity?

A

The minimum velocity required by an object to be able to escape a gravitational field of a mass when projected vertically from its surface.

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16
Q

What is Faraday’s Law?

A

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

17
Q

What is a field line/line of force?

A

A line representing the path that a North Pole (magnetic field), positive charge (electric field) or mass (gravitational field) would take when placed in the field.

18
Q

What is a force field?

A

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

19
Q

What is a geostationary satellite?

A

A satellite that orbits above the equator with a 24 hour period, so it will always remain above the same position on the Earth. They orbit approximately 36,000km above the surface of the Earth.

20
Q

What is a gravitational field?

A

A regional surrounding a mass in which any other object with mass will experience an attractive force.

21
Q

What is gravitational field strength?

A

The force per unit mass exerted on a small test mass placed within the field.

22
Q

What is gravitational potential energy?

A

The component of an object’s energy due to its position in a gravitational field.

23
Q

What is Kepler’s Third Law?

A

The square of an object’s orbital period (T) is directly proportional to the cube of its orbital radius.

24
Q

What is Lenz’s Law?

A

An induced current is always in a direction so as to oppose the change that caused it.

25
Q

What is a magnetic field?

A

A region surrounding a magnet or current-carrying wire that will exert a force on any other magnet of current-carrying wire placed within it.

26
Q

What is magnetic flux?

A

A value which describes the magnetic field or field lines passing through an area. It is the product of magnetic flux density and the perpendicular area it passes through.

27
Q

What is magnetic flux density?

A

The force per unit current per unit length on a current-carrying wire placed at 90° to the field lines. Sometimes also referred to as the magnetic field strength.

28
Q

What is magnetic flux linkage?

A

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

29
Q

What is the motor effect?

A

When a current-carrying wire is placed within a magnetic field (non-parallel to the field lines) and experiences a force perpendicular to both the wire and the field lines.

30
Q

What is the permittivity of free space?

A

A measure of the ability of a vacuum to allow an electric field to pass through it.

31
Q

What does polarised mean?

A

An atom/molecule becomes polarised when an external electric field causes the negative electron cloud to be shifted in the opposite direction to the positive nucleus - the charges are pulled in opposite directions. (This is what happens to the molecules of the dielectric in a capacitor).

32
Q

What is potential gradient?

A

The change of potential per metre at a point in the field.

33
Q

What is the radial field?

A

A field in which the field lines are all directed towards a single point (e.g. the centre of a planet or a point charge).

34
Q

What is relative permittivity?

A

The ratio of charge stored in a capacitor with the dielectric to charge stored without the dielectric. Also sometimes referred to as the dielectric constant.

35
Q

What is a step-down transformer?

A

A device made of two insulated wires coiled around an iron core in which the output voltage is smaller than the input outage due to the secondary coil having fewer turns than the primary coil.

36
Q

What is a step-up transformer?

A

A device made of two insulated wires coiled around an iron core in which the output voltage is greater than the input voltage due to the secondary coil having more turns than the primary coil.

37
Q

What is the synchronous orbit?

A

An orbit in which the period of the orbit is equal to the rotational period of the object that it is orbiting.

38
Q

What is the time constant?

A

The time taken for a capacitor to discharge 37% of its initial charge. The time constant is equal to the product of the capacitance and the resistance of the fixed resistor (that the capacitor is being discharged through).

39
Q

What is a uniform field?

A

A field in which all of the field lines are parallel and equally spaced - field strength is equal in all areas of the field.

Physics Definitions (9 decks)

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