Explanation questions
Often these type of questions are the most challenging and can make a difference to gaining better grades. The key to writing a good answer is to recognise and be clear about what area of the course the question is based on. This involves a good and ready knowledge of the course content based on effective revision.
- Once clear on the question being asked, plan the structure of an answer by listing keywords which will help to gain marks.
- Write a coherent and possibly concise answer with logical progression of what variable makes changes to others.
- Specify quantities e.g. âcapacitor voltageâ rather than just âvoltageâ.
- State or refer to any quantities that do not change.
- Donât use up/down arrows instead of the words increase or decrease in descriptions or explanations.
- Any question requiring a justification must have an attempt at justification to access the initial mark.
For example, if a question asks you to: "Explain the drop in terminal p.d. from a cell when a load resistance is connected":
- Consider what the physics is - internal resistance and the different voltages involved.
- Keywords will include internal resistance, lost volts, current and EMF.
- What is fixed - EMF and internal resistance.
- What changes and the order making reference to any relationships as appropriate.
Suggested answer
"When the load is connected the current drawn from the cell increases, which causes the lost volts across the fixed internal resistance to increase \((V_{L}=lr)\). Terminal p.d. is the difference between the fixed EMF and lost volts, so it reduces with increased current."