DP Physics (last assessment 2024)

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Question 22N.2.HL.TZ0.9c.i

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Date November 2022 Marks available [Maximum mark: 2] Reference code 22N.2.HL.TZ0.9c.i
Level HL Paper 2 Time zone TZ0
Command term Draw Question number c.i Adapted from N/A
c.i.
[Maximum mark: 2]
22N.2.HL.TZ0.9c.i

A parallel-plate capacitor of capacitance 1.5 × 10−10 F is made from two metal plates separated by an air gap of 1.0 mm. The capacitor is initially charged to a potential difference of 24 V.

The charged capacitor is disconnected from the voltage supply and the separation between the plates is increased to 4.0 mm.

The capacitor is then discharged through a fixed resistor. The initial current in the resistor is I0 and the time constant of the circuit is τ.

(c.i)

Draw, on the axes, a graph to show the variation with time of the current in the resistor.

[2]

Markscheme

exponential decrease from current = I0 ✓

approximately correct values for time = τ AND 2τ ✓

 

 

For MP2, the curve should be between 0.30 and 0.45 when time t = τ and below 0.20 when time t = 2τ.

Examiners report

The general shape of the curve was usually correct. Many candidates scored full marks, but the most common mistakes were ones that fell to 0.5 after one time constant, as if there was an attempt to identify a particular value, or fell far too steeply if not.

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