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Flashcards in Noir et Blanc Deck (17)
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How to convert from kelvin to degrees

subtract 273


How to convert from degrees to kelvin

Add 273


What is absolute zero? What is it in kelvin?

- The coldest anything can get, the particles has as little energy as is possible (-273 degrees)
- It is 0k


Explain why electrical energy is transmitted using a very high voltage. (5)

(M1) A high voltage leads to a low current
(M2) Because power = current x time
(M3) As a result, less energy is lost from the wire in the form of heat energy as the wires will not heat up as much due to a high current
(M4) This makes it more efficient
(M5) Because less current is flowing a thinner wire can be used without building up a large resistance


What is the unit for momentum?

kg m/s


What determines how much a wave is diffracted?

The wavelength of the wave compared with the size of thr gap.
- If the gap is much bigger than the wavelength there will be no diffraction.
- If the gap is the same as the wavelength then there will be maximum diffraction.


what are the two conditions needed for total internal reflection?

- Change in density of medium/ optically dense material
- The angle of incidence being larger than the critical angle


What happens is the angle of incidence is:
- less than the critical angle
- The same as
- Bigger than

- Less than: Rays are only partially internally reflected but most passes out
- Equal to: emerging ray comes out along the line of the surface and quite a lot is internally reflected
- More than: No light comes out. It is totally internally reflected.


Which device can be used to display sound waves?

An oscilloscope


What is the effect of a changing amplitude on a sound wave?

- The greater the amplitude of a wave or vibration, the more energy it carries.
- This means it will be louder.


Explain the connection between frequency and pitch in a sound wave.

- The frequency is the number of complete vibrations each second.
- If the wave vibrates with a high frequency, the sound is high pitched.
- If the wave vibrates with a low frequency, the sound is low-pitched.


Describe how to measure frequency on an oscilloscope.

- adjust the time division setting on the horizontal axis until the display shows at least one complete cycle
- Read off the time period (the time taken for one complete wave/ cycle to pass)
- Use equation frequency = 1/ time period to find the frequency


what is the key principle of friction?

Friction increases as speed increases


Describe what happens when a volt develops in a circuit.

FAULT - live wire touches the metal casing resulting in a big surge in current to the earth.
SURGE - this surge draws a large current through the live wire
The current raise the temperature of the circuit and the fuse melts
SAFETY - the fuse melting isolates the appliance from the live and so protects user from electric shocks.


What is the rule about current in a series circuit?

- The same current flows through each component
- Voltage is shared through the components


What is the rule of current in parallel circuits?

- The current is split
- The voltage is the same in each component.


What does a gold leaf electroscope do?

- It determines the size of the charge on an object by how much the gold leaf moves (i.e. how much it is repelled or attracted by the object)