A-LevelPhysicsElectricity9702/41 · Oct/Nov 2018 · Q58 Marks

The digital numbers shown in [Figure 5.1] are transmitted at a sampling rate of 500 Hz.

(a)State two advantages of the transmission of data in digital form, compared with the transmission in analogue form.[2]
(b)On [Figure 5.2], complete the graph to show the variation with time t of the signal level from the DAC.[4]
(c)(i)State the effect on the transmitted analogue signal when the sampling rate of the analogue-to-digital converter (ADC) and of the DAC is increased,[1]
(c)(ii)State the effect on the transmitted analogue signal when the number of bits in each sample is increased.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.

[B2] Any two reasonable suggestions e.g.: • noise can be eliminated/(signal/data) can be regenerated • bits can be added to correct for errors • data compression/multiplexing (is possible) • signal can be encrypted/better security
[B1] sketch: series of seven steps
[B1] each step width 2 ms
[A2] correct levels in correct order (2, 5, 14, 4, 9, 11, 7) (1 mark for 6 levels correct, 2 marks for 7 levels correct)
[B1] step width reduced or higher frequencies can be reproduced
[B1] step height reduced or smaller changes in signal (intensity) can be reproduced

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.