Electric circuits: distinguish voltage, current and resistance
Review six ideal-circuit tasks with Ohm relationships, series and parallel resistance, power and open paths. Paper examples with explicit assumptions.
This is a public learning guide, identical for everyone. A completed practice record separately shows correct, wrong and unanswered counts out of six for each part. These are not norms, ability ranks, official ASVAB scores or AFQT estimates.
The scope is an ideal written circuit
- This section uses voltage, current, resistance and power in small ideal models. It does not ask you to wire a circuit, handle a battery or test an electrical installation. The stated formulas and arrangements define each question. They are not a complete electronics curriculum and do not certify a person to work on an electrical system.
- Write the requested quantity and its unit before choosing an operation. Volts, amperes, ohms and watts describe different things. A plausible number with the wrong unit does not answer the question. Paper and a calculator are allowed, and the same six items are used in the timed and untimed modes.
A fresh Ohm calculation
- For an ideal 15 V source across one 5 ohm resistor, I = V/R gives 3 A. Check it by multiplying 3 A by 5 ohms to recover 15 V. Dividing the resistance by voltage produces the wrong relationship for the requested current, even if the arithmetic itself is performed accurately.
- The proportional relationship depends on the fixed-resistance, ohmic assumption. With the same resistor remaining ohmic, increasing voltage by a factor of three increases current by three. Actual devices can heat or behave nonlinearly; this exercise expressly stays inside the simplified model instead of treating every electrical component as an ideal resistor.
Identify the arrangement before adding
- In a series chain, the same current passes through the ideal resistors and their resistance values add. A 4 ohm resistor and an 8 ohm resistor therefore give 12 ohms. This addition belongs to the stated single path; seeing two resistors in a question does not automatically make every arrangement a series circuit.
- In parallel, branch voltages are equal and the reciprocal resistance contributions add. For 4 and 12 ohms, 1/R = 1/4 + 1/12 = 1/3, so R is 3 ohms. A useful check is that a parallel combination of positive resistances is lower than either branch. The reciprocal sum is not the resistance itself until inverted.
Power is a product, not an addition
- For a component with 6 V across it and 1.5 A through it, P = VI gives 9 W. The word across points to voltage, while through points to current. Keeping these two descriptions separate can make the equation easier to read. Adding 6 and 1.5 cannot yield electrical power because the quantities have different units.
- A watt describes a rate of energy transfer, not an amount of energy by itself. The practice does not supply operating temperatures, component ratings or safe loading conditions. A correct paper calculation cannot be used to select a real power supply or component without the additional engineering and safety information that this bank does not assess.
Trace the conducting path
- An open switch in the only ideal series path prevents steady current through the stated resistor. That conclusion follows from the complete arrangement given in the stem. Do not add an alternative branch, a hidden capacitor or an accidental contact that the question never specifies. A different circuit would require a different analysis.
- Zero current in this ideal paper problem is not a claim that a disconnected-looking real device is safe to touch. Real installations can have stored energy, other supplies and failure modes outside the question. Keep all practice hypothetical; this page provides no inspection, repair, mains-wiring or live-testing procedure.
A practical paper-study routine
- Choose a missed item and rewrite its known values, requested quantity, arrangement and assumption on four lines. Solve it without looking at the options. Then check a unit and a limiting relationship: for example, whether increasing fixed resistance should reduce current or whether adding a positive series resistor should increase total resistance.
- Create one fresh example with different values but the same arrangement. After solving it, change the arrangement from series to parallel and explain why the operation changes. This checks understanding of the connection rule instead of recall of a letter. It does not require building a physical circuit or buying any equipment.
Read the counts within their limits
- The six-item record separates selected correct answers, selected wrong answers and unanswered questions. It cannot establish why a miss occurred, compare electronics ability with other people or identify the weakest professional skill. All five complete study guides remain available, regardless of the count or chosen practice mode.
- These original questions are not official ASVAB items and have no calibrated score conversion. A repeated fixed-bank result may reflect memory or more time spent reading. Treat it as a local learning record, not proof of electrical competence, military qualification, an AFQT estimate or permission to undertake electrical work.