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Physics > Module 4 > Flashcards

Module 4 Flashcards

(54 cards)

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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

Study These Flashcards
A

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

23
Q

What is a light dependant resistor

Study These Flashcards
A

A resistor that decreases resistance for increasing light intensity

24
Q

What is a light dependant resistor

Study These Flashcards
A

A resistor that decreases resistance for increasing light intensity

25
Define electrical power
Rate of energy transfer by each electrical component
26
Define kilowhatt hour
Unit of energy (power x time)
27
What are lost volts
The difference between the terminal p.d. and the actual emf. emf = terminal pd + lost volts
28
What are the different components in emf=I(R+r)
R = Resistance of circuit r = internal resistance
29
How can Vout be varied
Variable resisitor
30
Define transvese wave
Oscilaltions are perpendicular to direction of energy They have peaks and troughs
31
Define longitudinal wave
Oscilations are parallel to direction of travel They have compressions and rarefractions
32
Define phase difference
Difference in displacement of particles along a wave measured in radians 360degrees = 2pi radians
33
Define antiphase
Phase difference of 180 degrees or pi radians
34
State the law of reflection
The angle of incidence is equal to the angle of reflection When waves are reflected their wavelength and frequency remain unchanged
35
Define refraction
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
Define intensity
Radiant power per unit area I i proportional to amplitude^2
37
What is an em wave
Wave that can travel through a vacuum
38
EM spectrum
Radio, Microwave, Infrared, Visable, ultraviolet, x-rays, Gamma.
39
Which em waves have the longest and shortest wavelength
Longest = radio Shortest = gamma
40
Wavelengths of visable light
700nm (red) 400nm (purple/ blue)
41
Refraction law when light travels from one medium to another
n1sin1 = n2sin2
42
When does total internal reflection occur
When light strikes the boundry above the critical angle Critical angle is measured against the normal
43
State the principle of superposition
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
Define coherence
2 waves having constant phase difference
45
When does destructive interference/minima occur
(n+0.5)wavelength
46
When does constructive interference/ maxima occur
(n)wavelength
47
What light is used in youngs double slit experiment
Monochromatic
48
Define node and antinode
Node is whewre two waves meet Antinode is where 2 waves are furthest apart
49
Define electron volt
The energy transferred to or from an electron when it moves though a potential difference.
50
What is the photoelectric effect
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
What did the gold leaf electroscope prove
How electrical charges repel each other
52
Define work function
Minimum energy required to free an electron from the surface of the metal
53
Are standing waves longitudinal or transverse
Longitudinal
54
What happens in a LDR
As light increases resistance decreases

Physics (26 decks)

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