The short answer
Voltage, current and resistance tied together by Ohm's law — and how series and parallel circuits differ.
Written and checked by GAMSAT tutors — not AI-generated.
Try the reasoning style
We treat forgetting as a failure — a lapse to be patched with reminders and records. Yet a mind that kept everything could not think; it would drown in the undifferentiated noise of every moment it had ever lived. To forget is not so much to lose information as to decide, mostly without our noticing, what was never worth keeping.
The author's argument relies most directly on which unstated assumption?
Pick an option to see how the tutor reasons to the answer — not just whether you were right.
Not quite — the answer is B.
Work backwards from the conclusion: a mind that ‘kept everything’ supposedly ‘could not think.’ That only follows if thinking means leaving most of experience out — so B is the premise the argument quietly rests on. A raises reliability, which the passage never weighs; C contradicts ‘mostly without our noticing’; D smuggles in a claim about intellect the passage never makes. The question rewards finding the hidden premise, not recalling a fact.
A circuit is plumbing for charge: voltage () pushes, resistance () restricts, and current () flows. One equation links them — Ohm's law, — and most circuit questions are just that plus knowing how series and parallel circuits behave.
The two equations
Ohm's law: (voltage = current × resistance). Power: . Rearrange Ohm's law as needed: and .
Series vs parallel
Series (one loop)
- Same CURRENT through every component
- Voltages ADD up
- Resistances ADD:
- One break stops the whole circuit
Parallel (branches)
- Same VOLTAGE across each branch
- Currents ADD up
- Total resistance is LESS than the smallest branch
The parallel-resistance trap
Adding resistors in parallel lowers the total resistance — it's always less than the smallest individual resistor, because you've given the current more paths to flow through. Many students wrongly expect resistance to go up.
Worked example
A 12 V battery drives two resistors, 4 Ω and 2 Ω, connected in series. What is the current in the circuit?
Check yourself
Two identical resistors are connected in parallel. Compared with one resistor alone, the total resistance is:
The paper prints one set of measurements and asks several questions on it, and the numbers rarely come out as clean as a textbook's — a real battery is not an ideal source. Below is that shape.
Passage· 3 questions on it
The following is adapted from a school physics practical.
| Arrangement | Lamps | Total resistance of the lamps (Ω) | Current from battery (A) | Terminal voltage (V) |
|---|---|---|---|---|
| I | one lamp | 6.0 | 1.85 | 11.1 |
| II | two in series | 12.0 | 0.96 | 11.5 |
| III | two in parallel | 3.0 | 3.43 | 10.3 |
| IV | three in parallel | 2.0 | 4.80 | 9.6 |
Q1 of 3 on this passage
Arrangement IV puts three 6.0 Ω lamps in parallel and the table gives their combined resistance as 2.0 Ω. Which statement explains that figure correctly?
Q2 of 3 on this passage
What is the resistance of the battery itself?
Q3 of 3 on this passage
Which arrangement delivers the most power to the lamps, and roughly how much?
Key takeaways
- Ohm's law: . Power: .
- Series: same current; voltages and resistances add.
- Parallel: same voltage; currents add; .
- Parallel resistance is always LESS than the smallest resistor.
- Find the total resistance first, then use Ohm's law for current.
Practise this with real GAMSAT-style questions
A timed diagnostic, real practice questions with worked explanations, and your first essay marked on our rubric built from ACER's two published criteria.