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A Level Physics OCR B > 2: Exam Questions > Flashcards

Flashcards in 2: Exam Questions Deck (12):

Calculating ratio, distance to A/distance to B (based on a given picture)

Image size ∝ 1/distance


Explaining minimum sampling freq.

high f are missed, aliases appear


Explaining why using only 'x' bits is sufficient

extra info is about details in noise not details in signal


Advantage and Disadvantage of using wider freq. range

Ad) higher quality speech, Dis) greater bandwidth


Digital samples can differ from the original analogue signals. How can you reduce that error?

1) more bits (per sample) 2) more sampling levels


Explain why something can take longer to download than calculated

more information has to be sent
explanation : possible bottleneck in named part of system /
recognise possible need for error checking /


Explain why a laptop will fail to communicate reliably with a hub beyond a certain distance. Consider signal strength and noise

signal decreases in amplitude as it spreads /
covers a wider area / signal gets absorbed by walls etc. ;
radio noise is present in environment ;
signal / noise ratio decreases as distance from hub
increases ;
noise may trigger false bits / degrade the signal
information / data link becomes inaccurate


A single musical note is played on an oboe. Amplitude against time graph given (regular large peaks with lots of 'wiggles' between large peaks):
State how the waveform shows that the note has a definite pitch but that it also contains more than 1 freq. component [2]

waveform is periodic / (main peaks) repeats itself regularly ;

but more complex than pure sine wave / has harmonics /
higher frequency (oscillations) / other (smaller) oscillations /
smaller peaks (between large ones)


Describe how you would estimate the bandwidth needed for transmitting the digitised information (freq. given, bits per sample given)

bandwidth ≈ bit rate / ≈ bit rate /2
bit rate = sampling frequency x bits per sample


[1] state what is meant by the resolution of a measuring instrument

smallest difference that can be detected


[1] One application of an ammeter is to monitor a current to check that it does not suddenly increase to a much larger value. Explain why the analogue ammeter may be a better choice than the digital ammeter

Easier to see sudden movement of needle than changes in
digits/ digital meter samples/has time lag (1)


Suggest why an ammeter for use in circuits carrying large currents should have a very low resistance [1]

one of:
Idea of not affecting the measurement (1);
Meter will overheat and could be damaged (1);
smaller p.d. drop across the resistor (1)