AQA Exam -- oscilloscope question concept

[bonbon22]

Homework Statement

aqa paper question images below
https://filestore.aqa.org.uk/sample-papers-and-mark-schemes/2017/june/AQA-74083A-QP-JUN17.PDF
3.2 question

Relevant Equations

no relevant equation i think

can anyone explain why the voltage reading is negative for the resistor over a time period , yet the capacitor reading always stays positive ?
In AC generation the voltages goes from negative to positive, how exactly does this affect the circuit components voltages? I am not sure how AC affects the components of the circuit When charging and discharging? i understand that the capacitor is charging and discharging and the general shape of the curve.
thank you in advance

 

[scottdave]

Think about which way the current is flowing as the charged capacitor now discharges through the resistor (during the time when generator is at zero volts)

 

[bonbon22]

Think about which way the current is flowing as the charged capacitor now discharges through the resistor (during the time when generator is at zero volts)

upwards? Is the voltage direction of the resistor always opposite to the capacitor?
essentially does the resistor current flow in the opposite direction to the capacitors?

 

[scottdave]

Please don't think of voltage as having a "direction". Given a certain reference point, another point may have higher or lower voltage than the reference. This would read as a positive or negative voltage. You need to note that the oscilloscope has moved it's reference point. The voltage at the "top" of the resistor is equal to the output voltage of the signal generator in this circuit (when the switch is closed). So think about how the oscope is measuring across the resistor.

 

[mjc123]

Are you sure the circuit in Figure 9 (question 02.3) applies to question 02.6? It says the waveform is shown in Figure 10 (not Figure 12). Question 02.6 is not about AC (a sinusoidal waveform), it is a voltage alternating between a constant positive value and zero.