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Physics > Electricity > Flashcards

Electricity Flashcards

1
Q

Electric Charge

A

Indicate if a body has an excess or a deficiency of electrons

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2
Q

Electrostatics

A

The properties of charge particles at rest

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3
Q

Negative charge

A

When an object gains electrons.
Polythene when rubbed a dry cloth

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4
Q

Positive charge

A

When an object loses electrons
Perspex when rubbed with a dry cloth

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5
Q

Point discharge

A

Where ions in the air either strongly attracted or appelled from the tip of a charged conductor and move towards or away from it

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6
Q

Coulomb’s law

A

The force between two point charges is directly proportional to the product of the charges at inversely proportional to the square of the distances between them

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7
Q

Electric field

A

The region of space in which electric forces can be felt

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8
Q

Electric field line

A

The line along which a positive charge would move if placed in the electric field

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9
Q

Electric field strength

A

Add a points in the electric field it is the force experienced per unit charged placed at that point in the field
E = F/Q

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10
Q

Potential difference (V)

A

The work done in moving a charge of one coulomb from 1point to another
V = W/Q

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11
Q

Insulator

A

A substance through which electric charge cannot flow

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12
Q

Conductor

A

A substance through which electric charge can flow

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13
Q

Coulomb

A

Unit for electric charge. One coulomb of charge passes a particular point when a current of 1 A flows for 1 second

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14
Q

1 Volt

A

The potential difference between two points if one Joule of work is done in bringing one coulomb of charge from one point to the other

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15
Q

Capacitance

A

The ratio of charge to voltage in a conductor
C = Q / V

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16
Q

Emf

A

Electromotive Force. The voltage applied to a circuit

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17
Q

Capacitor

A

An electrical device capable of storing electric charge

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18
Q

Farad

A

A capacitor has a capacitance of 1 farad, if by placing a charge of 1 coulomb on it raises it potential by 1 volt
1 F = 1 C/V

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19
Q

Resistance

A

The ratio of voltage across an object to the current flowing through it
R=V/I

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20
Q

Resistor

A

A device that converts electrical potential energy to some other form

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21
Q

Resistivity

A

A constant associated with resistance of a body. Equal to the product of the resistance of the body and its cross-sectional area divided by its length

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22
Q

Potential at a point

A

The difference in the potential at a given point and potential of the earth (take it to be 0)

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23
Q

Current

A

The rate of flow of charge
I = Q/t

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24
Q

Ammeter

A

A device that measures current. Must be connected in series

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25
Q

Voltmeter

A

Advice that measures potential difference across a component must be connected in parallel or across the component

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26
Q

AC vs DC

A

DC always flows in one direction, AC constantly changes direction

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27
Q

Ohm

A

Unit of resistance. Conductor has resistance of 1 ohm if a current of 1A passes through when a potential difference of 1V is applied

28
Q

Ohm’s Law

A

The current flowing through conductor is directly proportional to the potential difference across it, if the temperature remains constant
V = IR

29
Q

Joules Law

A

The rate of heat produced in a conductor is proportional to the square of the current flowing through it

30
Q

Ion

A

An atom or group of atoms that has lost or gained one or more electrons

31
Q

Electrolysis

A

The passing of an electric current true or liquid causing a chemical reaction

32
Q

Fuse

A

A safety device consisting of a piece of wire which melts when a current above a preset value passes through it

33
Q

MCB

A

Miniature circuit breaker. A safety device which breaks the circuit if it takes a current above a preset value

34
Q

RCD

A

Residual current device. A safety device that breaks the circuit if it detects a current difference between live and neutral above a preset value

35
Q

Radial Circuit

A

When a separate life and neutral wire are connected from the distribution box to an appliance which uses large current. E.g. electric cooker

36
Q

Ring circuit

A

When the tree terminals of each socket (live, neutral and earth) are connected to three corresponding wires arranged in a ring or loop with each of the rings connect to the distribution box

37
Q

Bonding

A

A safety precaution whereby all metal pipes taps and tanks are earthed

38
Q

1 kWh

A

1 kilowatt hour full stop the amount of energy used by 1000 watt appliance in one hour

39
Q

Semiconductor

A

A substance whose resistivity is between that of a good conductor and a good insulator. The resistivity decreases of the temperature increases

40
Q

Holes

A

Positively charged gaps or spaces in a substance which are created when electrons break free from covalent bonds

41
Q

Intrinsic conduction

A

Occurs in a pure semiconductor when there are an equal number of electrons moving from negative to positive and holes moving in the opposite direction. The movement of charge through a pure semiconductor

42
Q

Doping

A

The addition of impurities to a semiconductor to increase its conductivity

43
Q

Extrinsic conduction

A

An increased rate of conduction due to the addition of impurities. The movement of charge through a doped semiconductor

44
Q

N-Type semiconductor

A

A semiconductor in which the impurity added produces more free electrons available for conduction

45
Q

P-Type Semiconductor

A

Semiconductor in which the impurity added produces extra holes available for conduction

46
Q

Diode (p-n junction)

A

A semiconductor device that allows current to flow in one direction only

47
Q

LDR

A

Light dependent resistor. A semiconductor who’s resistance decreases as light intensity increases

48
Q

Thermistor

A

A semiconductor whose resistance decreases rapidly with increasing temperature

49
Q

Ampere

A

The constant current that, if maintained in two straight parallel conductors of infinite length, of negligible cross-section, and placed 1 meter part in a vacuum would produce a force on each conductor of 2 x 10-⁷ newtons per meter of length

50
Q

Magnetism

A

A phenomenon by which certain metals exert attractive or repulsive forces on other metals

51
Q

Magnetic field

A

A region of space in which magnetic forces can be felt

52
Q

Magnetic Field line

A

Indicates the direction magnetic north would travel in the magnetic field if it was free to do so

53
Q

Fleming’s left hand rule

A

If the thumb, index finger and second fingers are held it right angles to each other, with index finger pointing in the direction of the magnetic field and the second finger pointing in the direction of the current then the thumb points in the direction of the force

54
Q

Magnetic flux

A

Total amount of magnetic field in a given region. Product of magnetic flux density and area

55
Q

Magnetic flux density (B)

A

At a point in a magnetic field it is a vector whose magnitude is equal to the force experience by conductor of length 1 m, carrying a current of 1A, right angles to the field at that point and who’s direction is is the direction of the magnetic field lines

56
Q

1 Tesla

A

The magnetic flux density at a point if a conductor of length 1 m, carrying a current of 1A, experiences of force of 1 N when placed at right angles to the field

57
Q

1 Weber

A

The magnetic flux over an area of 1 m² if place in a field of magnetic flux density of 1 Tesla

58
Q

Electromagnet

A

Consists of a solenoid with a soft iron core. When current is passed through the solenoid, the core becomes magnetic. When the current is switched off, the core loses its magnetism

59
Q

Electromagnetic induction

A

The inducing of an EMF by changing the magnetic flux in a closed loop

60
Q

Laws of electromagnetic induction

A

Lenz’s law
Faraday’s law

61
Q

Faraday’s Law

A

The size of the induced EMF is proportional to the rate of change of magnetic flux linking the circuit

62
Q

Lenz’s Law

A

The direction of an induced EMF opposes the change causing it

63
Q

Mutual induction

A

Occurs in two adjacent coils when the magnetic field in one coil changes at an EMF is induced in the other

64
Q

Self Induction

A

When a changing magnetic field in a coil induces an EMF in the coil itself

65
Q

Transformer

A

An electrical device used to change the voltage of AC power supplies

66
Q

Inductor

A

An electrical device used to induce a back EMF

67
Q

Electrical generator

A

A device which converts mechanical energy to electrical energy by electromagnetic induction

Physics (6 decks)

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