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Physics > Module 4 > Flashcards

Module 4 Flashcards

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1
Q

Define electric current

A

Rate of flow of charge

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2
Q

Why is charge quantized

A

It is always a multiple of e

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3
Q

Define electrolyte

A

Liquid that conducts electricty

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4
Q

How does a liquid conduct electricity

A

Ions

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5
Q

What charge is an anode

A

Positive

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6
Q

What charge is a cathode

A

Negative

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7
Q

Kirchoffs First law

A

For any point in an electrical circuit, the sum of the currents into that point is equal to the sum of the currents out of that point (conservation of charge)

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8
Q

Define conductor

A

High number density
10^28 (free electrosn per meter cubed)

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9
Q

Define insulator

A

Low number density

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10
Q

Define semi- conductor

A

Number density around 10^17
In order to carry the same current, the electrons must move faster so the material becomes hotter

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11
Q

What is v in I=Anev

A

Mean drift velocity

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12
Q

Define electromotive forcce (emf)

A

Describes work done on the charge carriers

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13
Q

Define potential difference

A

Work done by the charge carriers

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14
Q

Define thermionic emmision

A

The emmission of electrons through the action of heat

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15
Q

Define ohms law

A

For a metallic conductor kept at a constatnt temperature, the current in the wire is directly proportional to the p.d. accross its ends

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16
Q

What are the I - V characteristics of a resistor

A

Obeys ohms law (ohmic conductor)
the resistor behaves the sme regardless of polarity

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17
Q

What are the I - V characteristics of a filament lamp

A

Non-ohmic component
The resistance is not constant
Behaves the same regardless of polarity

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18
Q

What are the I - V characteristics of an LED

A

Non-ohmic component
The resistance is not constant
The diodes behaviour depends on the polarity
Resistance decreases at threshhold p.d. and light is emitted

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19
Q

Resistivity of conductors

A

10^8 ohmmmeters

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20
Q

Resisitivity of insulators

A

10^16 Ohmmeters

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21
Q

What is a negative temperature coefficient

A

Resistance drops as temperature increases (thermistor)

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22
Q

What are the I- V characteristics of a thermistor

A

Non ohmic component
The resistance is not constant
Behaves the same regardless of polarity

23
Q

What is a light dependant resistor

A

A resistor that decreases resistance for increasing light intensity

24
Q

What is a light dependant resistor

A

A resistor that decreases resistance for increasing light intensity

25
Q

Define electrical power

A

Rate of energy transfer by each electrical component

26
Q

Define kilowhatt hour

A

Unit of energy (power x time)

27
Q

What are lost volts

A

The difference between the terminal p.d. and the actual emf.
emf = terminal pd + lost volts

28
Q

What are the different components in emf=I(R+r)

A

R = Resistance of circuit
r = internal resistance

29
Q

How can Vout be varied

A

Variable resisitor

30
Q

Define transvese wave

A

Oscilaltions are perpendicular to direction of energy
They have peaks and troughs

31
Q

Define longitudinal wave

A

Oscilations are parallel to direction of travel
They have compressions and rarefractions

32
Q

Define phase difference

A

Difference in displacement of particles along a wave measured in radians
360degrees = 2pi radians

33
Q

Define antiphase

A

Phase difference of 180 degrees or pi radians

34
Q

State the law of reflection

A

The angle of incidence is equal to the angle of reflection
When waves are reflected their wavelength and frequency remain unchanged

35
Q

Define refraction

A

When a wave changes direction as it changes speed when passing from one medium to another
whenever there is refraction there is partial reflection

36
Q

Define intensity

A

Radiant power per unit area
I i proportional to amplitude^2

37
Q

What is an em wave

A

Wave that can travel through a vacuum

38
Q

EM spectrum

A

Radio, Microwave, Infrared, Visable, ultraviolet, x-rays, Gamma.

39
Q

Which em waves have the longest and shortest wavelength

A

Longest = radio
Shortest = gamma

40
Q

Wavelengths of visable light

A

700nm (red)
400nm (purple/ blue)

41
Q

Refraction law when light travels from one medium to another

A

n1sin1 = n2sin2

42
Q

When does total internal reflection occur

A

When light strikes the boundry above the critical angle
Critical angle is measured against the normal

43
Q

State the principle of superposition

A

When two waves meet at a point, the resultant displacement at that point is equal to the sum of the displacements of the individual waves

44
Q

Define coherence

A

2 waves having constant phase difference

45
Q

When does destructive interference/minima occur

A

(n+0.5)wavelength

46
Q

When does constructive interference/ maxima occur

A

(n)wavelength

47
Q

What light is used in youngs double slit experiment

A

Monochromatic

48
Q

Define node and antinode

A

Node is whewre two waves meet
Antinode is where 2 waves are furthest apart

49
Q

Define electron volt

A

The energy transferred to or from an electron when it moves though a potential difference.

50
Q

What is the photoelectric effect

A

High energy electromagnetic radiation causes electrons to be emmitted from the surface of a metal
Electrons only emitted if incident radiation was above the threshold frequency

51
Q

What did the gold leaf electroscope prove

A

How electrical charges repel each other

52
Q

Define work function

A

Minimum energy required to free an electron from the surface of the metal

53
Q

Are standing waves longitudinal or transverse

A

Longitudinal

54
Q

What happens in a LDR

A

As light increases resistance decreases

Physics (26 decks)

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