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Page 1

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Current:

- Flow of charge per unit time
o Electrons in metals, ions in electrolyte
- Conventional current ­ a model used to describe the movement of charge in a circuit (positive to
negative)
- Electron flow ­ the movement of electrons around a circuit (negative to positive)
- One…

Page 2

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- Number densities ­ if low electrons have more space to move and collide with each other less
resulting in higher drift velocities

Potential Difference (p.d.):

- Energy transferred per unit charge, when electrical energy is converted to another type
- One Volt = one Joule per Coulomb
- Voltmeter…

Page 3

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Experiment to determine I/V characteristics:

- Vary current and p.d. using variable resistor
- Record current and p.d. from ammeter and voltmeter
- Plot I/V graph
- Resistance = gradient-1

Light Emitting Diodes (LEDs):

- Only allow current to flow in one direction and emit light when
a p.d. is…

Page 4

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Negative Temperature Coefficient (NTC) as is for semiconductors:

- A thermistor has a NTC ­ when heated electrons in the thermistor gain enough energy to escape the
metal lattice
- This increases the number of charge carriers available (increasing n) which causes a fall in resistance
- Light dependent resistors…

Page 5

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- Advantages :
o If a continuous record of temperature or light intensity is needed, you can connect a data
logger to the thermistor or LDR because they produce electrical outputs
o eliminate the chance of human error in the calculations
o Can plot accurate graphs straight away
o Very…

Page 6

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Progressive wave:

- A wave that transfers energy from one place to another

- Wave speed ­ the speed at which energy is transmitted by a wave v = f

Refraction:

- Change in direction of a wave as it crosses an interface between two
materials where its speed changes…

Page 7

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Ultraviolet:

- All can damage the eyes
- UV-A
o 99% of UV, causes tanning and wrinkles
- UV-B
o Can cause DNA in skin to become damaged causing skin cancer
- UV-C
o Absorbed by the ozone layer

Polarisation of waves:

- If a transverse wave is incident on…

Page 8

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Experiment to show two source interference:

- When two loudspeakers are connected to the same signal generator, their signals interact this can
be heard as you walk in front of the loudspeakers. You will hear a loud sound where the sound
waves reinforce one another (constructive), and at other points…

Page 9

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o In a progressive wave every point oscillates with the same amplitude and every point
oscillates, stationary waves have nodes and antinodes
o In progressive waves all points have a different phase
- Harmonics
o Fundamental mode of vibration ­ lowest frequency stationary wave for a particular
system (first harmonic)…

Page 10

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o Only photons with energy > cause electron emission
o (work function) is the minimum energy required to release electrons
o Number of electrons emitted depends upon light intensity, as long as energy is greater than
the work function
o Emission is instantaneous and photons transfer all or none of…

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