"Most Challenging" A Level Physics Question

Electric Fields Revision Question from the 2021 OCR Physics A Exploring Physics Paper 2 Solutions on Electric Fields. Paper: https://www.ocr.org.uk/Images/667296-... According to the examiner report, Q4, Q5 and Q12 were "most challenging" and this is one of them. Here is the examiner's report: https://www.ocr.org.uk/Images/670953-... This question is excellent physics revision for all exam boards including OCR Physics A, OCR Physics B, AQA Physics, Edexcel Physics, Cambridge International and others.