These questions probe pupils’ understanding of the behaviour of simple electric circuits. Most are about series circuits, and check that pupils understand the relationships between the battery voltage and the current, and between the resistance in the circuit and the current. We have found Q5 in this set poses particular problems for pupils – many of whom think that one ammeter reading will decrease but the other will stay the same. (This really goes back to their understanding of current as a ‘conserved’ quantity in a series circuit.)
Qs7-10 probe understanding of the effect of adding a resistor in series or parallel to one already present. We have found that very few pupils can answer correctly about the parallel combinations; they seem not to ‘see’ this as providing an additional route for current, thus making the resistance less (and the current from the battery bigger). This is a point worth drawing attention to in teaching – having a ‘picture’ in your mind of what is going on is likely to be more useful than trying to remember the ‘rules’!