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Physics > Electric and Magnetic Fields > Flashcards

Electric and Magnetic Fields Flashcards

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0
Q

Define electric field strength.

A

Force per unit positive charge

E = F/Q

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1
Q

What unit is used for electric field strength?

A

N C^-1

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2
Q

Potential gradient =

A

Electric field strength

V/d

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3
Q

What creates electric fields?

A

Electric charges

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4
Q

Unit for magnetic flux

A

Weber - Wb

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5
Q

Unit for magnetic flux density

A

Tesla

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6
Q

Faraday’s Law of electromagnetic induction

A

The magnitude of induced e.m.f. is equal to the rate at which the magnetic flux is cut

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7
Q

Lenz’s Law

A

The direction of any induced current is in a direction that opposes the flux change that causes it

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8
Q

A.C. Generator

A

A generator that, via the use of slip rings, produces an alternating e.m.f. and so an alternating current

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9
Q

Alternating current

A

Electric current that reverses its direction with a constant frequency.

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10
Q

Ammeter

A

A device used to measure electric current, connected in series with the components

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11
Q

Conductor

A

A material with a high number density of conduction electrons and therefore a low resistance

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12
Q

Conventional current

A

A model used to describe the movement of charge in a circuit.

Conventional current travels from + to -

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13
Q

Coulomb’s law

A

The force between to charges is proportional to the product of the charges and inversely proportional to the square of the distance between the charges

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14
Q

Efficiency

A

The ratio of useful output energy to total input energy

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15
Q

Electric charge (Q or q)

A

Current x Time

Measured in Coulombs (C). Scalar quantity

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16
Q

Electric current

A

A flow of charge

Vector quantity, measured in amperes (A)

17
Q

Electric field strength (E)

A

Force per unit charge

Given by E=F/q

Measured in N C^-1

18
Q

Electric field

A

A region of space where a charged particle experiences a force

It goes from + to -

19
Q

Electromagnetic Induction

A

The process of inducing e.m.f. using a magnetic field and a changing flux linkage

20
Q

Electromagnetic wave

A

A self-propagating wave that does not require a medium to travel through

21
Q

E.m.f.

A

The electrical energy transferred per unit charge when one form of energy is converted into electrical energy

Measured in volts (V)

22
Q

Electron flow

A

The movement of electrons (usually around a circuit), from - to +

23
Q

Electronvolt

A

One electronvolt is the energy change of an electron when in moves through a potential difference of one volt

24
Q

Fleming’s LEFT hand rule

A

Used with electric motors and forces acting on moving charges in magnetic fields

It shows the direction of force on a conductor carrying a current in a magnetic field.

Force - thumb, field - first finger, current - second finger, all at right angles to each other

25
Q

Fleming’s RIGHT hand rule

A

Used with generators and electromagnetic induction

It shows the direction of the induced current when a conductor moves through a magnetic field

Force - thumb, field - first finger, current - second finger, all at right angels to each other

26
Q

Induced e.m.f.

A

The e.m.f. produced by electromagnetic induction

27
Q

Insulator

A

A material with a small number density of conduction electrons and therefore high resistance

28
Q

Lenz’s law

A

When a magnet is moved in a coil of wire, the coil has an induced e.m.f.

If connected in a circuit, the coil itself produces a magnetic field. This magnetic field opposes the magnet

29
Q

Define magnetic flux

A

The product of magnetic flux density and the area at right angles to the flux

30
Q

Define ampere

A

SI unit for electric current

31
Q

What is alternating current?

A

Electric current that reverses its direction with a constant frequency

32
Q

What is an a.c. generator?

A

A generator that, via the use of slip rings, produces an alternating emf and so an alternating current

33
Q

Define magnetic flux density

A

The strength of the magnetic field

34
Q

Define magnetic flux

A

The product of magnetic flux density normal to a circuit and the cross-sectional area of the circuit.

35
Q

Define magnetic flux linkage

A

The product of the magnetic flux and the number of turns

36
Q

Define intensity

A

Power per unit cross-sectional area

37
Q

Define what is meant by a uniform electric field

A

A region between two objects of different electric potential in which a charged particle will feel a force and the strength of the force is the same at any point in the field.

Field lines are equispaced.

38
Q

What is a magnetic field?

A

Region where a force is exerted on magnetic material

Field lines go from north south (direction a north pole would feel a force in the field).

39
Q

What is the law of conservation of charge?

A

Electric charge cannot be created or destroyed

Positive and negative charges can make each other neutral

Physics (9 decks)

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