Paper 1 DC Circuits Answers

Q	Ans	Brief reason
1	A	Series current is common.
2	A	Parallel branches share nodes.
3	C	Series resistances add.
4	A	Reciprocal sum gives $2\Omega$.
5	A	Ammeter should not add significant resistance.
6	B	Voltmeter draws negligible current.
7	A	Divider formula.
8	A	Larger fraction of source p.d. appears across lower resistor.
9	B	Detector current is zero at balance.
10	A	No current means equal opposing p.d.s.
11	B	Low-resistance bypass.
12	A	Break prevents current.
13	A	Brightness tracks power approximately.
14	A	Series adds resistance.
15	B	Parallel adds conducting path.
16	A	Charge conservation.
17	A	Energy per unit charge conservation.
18	A	NTC thermistor behaviour.
19	A	LDR behaviour.
20	A	High series resistance greatly reduces current.