G3 SEC EMS Variable-Load Decision Guide

Quick answer: The fictional alternative B reduces four-hour line-heating energy from 144 Wh to 81 Wh, a real 43.75% modelled reduction. But it also reduces receiver delivery from 240 Wh to 207 Wh. Therefore the headline “43.75% less waste with the same useful output” is not supported. Always audit the complete source–line–receiver ledger before claiming a fair improvement.

This final guide in the four-volume sequence combines G3 Physics, Mathematics and English to test whether a public statement follows from a calculation. The scenario is invented, text-only and not electrical safety guidance. The aim is precise examination reasoning, not the design or installation of a power system.

2027 G3 SEC English K300, Mathematics K310 and Physics K323 are separate official subjects
Rebuild A and B with a fixed 24 V source, 2 Ω line and four-hour variable currents
Calculate line heating, source energy and receiver delivery rather than one attractive percentage
Explain how a higher percentage share can hide a lower absolute outcome
Rewrite unsupported claims with specific conditions and clear English
Use independent questions, worked solutions and a four-week transfer plan

A decision before a headline
What learners should be able to decide
Keep the official SEC boundary clear
Read the problem statement as a contract
The Physics calculation begins with heating
Time weighting turns three rates into one total
The source and receiver are different boundaries
Finish the original energy ledger
Introduce B without pretending it is the same service
The new line-heating energy really is lower
A source-energy comparison changes the story
Calculate what reached the receiver in B
The trade-off is visible in three differences
Percentages need a noun and a denominator
The surprising result: a larger delivered share, less delivered energy
Percentage points are not percentage changes
Why case B cannot inherit case A’s service
What if the line resistance were changed instead?
An honest claim register for a public report
Do not turn an educational table into electrical instructions
The English problem: a sentence may be grammatical but false
Rewrite one headline with minimal distortion
A reader-safe public paragraph
Present the numbers in a text-only decision table
Check the three types of evidence
An uncertainty question that the table cannot settle
Inspect the result from the other direction
A conflict between true numbers and a false promise
How this connects to Physics assessment
How this connects to Mathematics assessment
How this connects to English assessment
A ten-minute evidence-hearing routine
An independent four-week revision plan
Parents and tutors: ask for an explanation, not a slogan
Independent evidence-hearing questions and worked answers
Frequently asked questions
Official references and previous learning routes

A decision before a headline

A fictional school committee receives two energy-model summaries. The first says that its original four-hour model loses 144 watt-hours as heat in a cable. The second says that a changed model loses only 81 watt-hours, a reduction of 43.75%. Someone drafts the headline “Same electricity delivered, with 43.75% less waste.” The arithmetic about cable heating is correct, but the claim about identical delivery is not. The changed model also carries less electrical energy to the receiver. This guide is about finding that difference before a public statement becomes misleading. We will use Physics for energy transfers, Mathematics for comparisons and English for precise conclusions. The setting and every figure are invented for learning, not obtained from an actual school, electrical installation or examination paper.

What learners should be able to decide

By the end, you should be able to reconstruct each row of the two alternatives, compare their totals on a common four-hour basis, test a percentage statement against its denominator and state whether the evidence supports equal useful output. You should also be able to reject a grammatical edit that is only a stylistic preference, explain the limits of an electrical teaching model, and write a concise conclusion for a reader who has not seen the calculations. These are transferable examination habits. They help with Physics explanations, Mathematics real-world problems, and English Writing or Comprehension, but they do not form a separate SEC subject called EMS. The examination assesses those subjects under their own requirements.

Keep the official SEC boundary clear

The first SEC examination is in 2027 and offers subjects at G1, G2 and G3. On SEAB’s 2027 G3 list, English Language is K300, Mathematics is K310 and Physics is K323. The older reference codes are 1184, 4052 and 6091 respectively. A student taking Combined Science follows a different syllabus and code from a student taking standalone Physics. This article uses ideas connected to the Physics syllabus, along with Mathematics and English skills; it does not claim that the three subjects share one assessed task. The exact examination papers, lengths, weightings and permitted materials should always be checked against the student’s own current SEAB subject syllabus. Our integrated activity is a study method, not a prediction of a paper question.

Read the problem statement as a contract

Our fictional model has an idealised source held at 24 volts and a line of constant resistance 2 ohms. Current varies during a four-hour period. The three operating intervals are one hour at 2 amperes, two hours at 4 amperes and one hour at 6 amperes. Assume a simple model in which source power is divided between the heating of the line and power delivered to a passive receiver. No other pathway is included. The source voltage and line resistance are held constant within this original model. Those statements define the contract for every equation that follows. If the source voltage, resistance, receiver behaviour or duration changes, the conclusion must be recalculated rather than copied from the original table.

The Physics calculation begins with heating

The electrical heating rate in the modelled resistive line is given by P = I²R. At 2 A and 2 Ω the rate is 8 W. At 4 A it is 32 W. At 6 A it is 72 W. The square means that the last current, three times the first, gives nine times the line-heating power at unchanged resistance. The formula calculates power, which is a rate of energy transfer. It does not by itself give the energy used during an entire period. The data represent stipulated values rather than measured current from a physical installation. A responsible scientific answer tells the reader both the equation and the conditions under which it is being applied.

Time weighting turns three rates into one total

Multiply each loss power by the duration for which it applies. The first interval loses 8 W multiplied by one hour, giving 8 Wh. The two-hour middle interval loses 32 W multiplied by two hours, giving 64 Wh. The final interval loses 72 W multiplied by one hour, giving 72 Wh. Together they make 144 Wh or 0.144 kWh of line heating in four hours. The duration-weighted mean rate is 144 Wh divided by four hours, or 36 W. A casual calculation that squares the average current of 4 A and obtains 32 W will be wrong because squaring and averaging cannot generally be interchanged. The energy ledger must be built one interval at a time.

The source and receiver are different boundaries

The source supplies electrical power at 24 V times the current. Its powers across the intervals are 48 W, 96 W and 144 W. The line voltage drops are IR, giving 4 V, 8 V and 12 V. The remaining voltages across the receiver are 20 V, 16 V and 12 V. Multiplying each receiver voltage by the corresponding current gives useful receiver powers of 40 W, 64 W and 72 W. In each row, source power equals line heating plus receiver power: 48 = 8 + 40, 96 = 32 + 64, and 144 = 72 + 72. Calling all of these figures “consumption” would conceal the different physical boundaries. Name the component or boundary every time.

Finish the original energy ledger

Over the stated durations, source energy is 48 × 1 + 96 × 2 + 144 × 1 = 384 Wh. Receiver energy is 40 × 1 + 64 × 2 + 72 × 1 = 240 Wh. Line-heating energy is 144 Wh. The check 384 = 240 + 144 confirms that the simple two-destination model is internally consistent. This is the reference case, or A. The receiver obtained 240 Wh, and the line converted 144 Wh to heat. Those facts must travel together if another case is compared with A. A statement about reduced waste that omits what happened to the receiver’s energy may hide an important change in service.

Introduce B without pretending it is the same service

Alternative B stipulates that every current is multiplied by 0.75. The new values are 1.5 A for one hour, 3 A for two hours and 4.5 A for one hour. Source voltage remains 24 V, line resistance remains 2 Ω, and durations stay the same. Because the currents change, the receiver powers change under the fixed-source model. No school device has been shown to perform an identical task at the new current values. This is a hypothetical parameter comparison, not a replacement that promises equal lighting, equal work or equal comfort. Write that qualification at the moment B is introduced. Waiting until the conclusion makes it too easy for an unsupported headline to appear between the numbers and the reader.

The new line-heating energy really is lower

At 1.5 A, line power is 2 × 1.5² = 4.5 W, giving 4.5 Wh in one hour. At 3 A, line power is 18 W, giving 36 Wh over two hours. At 4.5 A, line power is 40.5 W, giving 40.5 Wh over one hour. The total is 81 Wh. Subtracting it from A’s 144 Wh produces 63 Wh less heating. The percentage reduction uses the original as denominator: 63 divided by 144 multiplied by 100, or 43.75%. This is a correct, exact statement about line heating in the invented four-hour model. It is not yet a conclusion about the receiver, school electricity costs or emissions.

A source-energy comparison changes the story

In B, the source still provides 24 V, but the currents are smaller. Source powers are therefore 36 W, 72 W and 108 W. Applying the durations gives 36 Wh + 144 Wh + 108 Wh = 288 Wh. In A, the source supplied 384 Wh. B therefore draws 96 Wh less from the modelled source across four hours, which is a 25% decrease relative to A. This percentage is different from the 43.75% fall in line heating. Both percentages are accurate, but they describe different numerators. Do not replace one with the other. Before writing “electricity saved”, specify what energy entered the chosen source boundary and what, if anything, was delivered to the receiver.

Calculate what reached the receiver in B

For B, subtract each interval’s line-heating power from its source power. The receiver receives 36 − 4.5 = 31.5 W in the first hour, 72 − 18 = 54 W during the two-hour middle interval, and 108 − 40.5 = 67.5 W in the final hour. Receiver energy is therefore 31.5 × 1 + 54 × 2 + 67.5 × 1 = 207 Wh. The independent ledger check is 288 Wh at the source equals 81 Wh lost in the line plus 207 Wh delivered to the receiver. The new total is not 240 Wh, so the proposed “same electricity delivered” claim fails even within the simple model. We did not need advanced theory to find this: we needed a complete ledger.

The trade-off is visible in three differences

Compared with A, case B supplies 96 Wh less source energy, converts 63 Wh less to line heat, and delivers 33 Wh less to the receiver. The three differences fit together: the 96 Wh reduction in source energy consists of a 63 Wh reduction in line heating and a 33 Wh reduction in receiver energy. That is an especially useful cross-check. A draft that boasts of 63 Wh less waste but ignores 33 Wh less delivery is selecting only the favourable part of the story. Neither figure has to be described as inherently good or bad; the user of the model must first decide what service is required. A fair conclusion reports both the gain and the trade-off.

Percentages need a noun and a denominator

The 63 Wh loss reduction is 43.75% of A’s 144 Wh line heating. The 96 Wh source reduction is 25% of A’s 384 Wh source energy. The 33 Wh reduction in receiver delivery is 13.75% of A’s 240 Wh receiver energy. All three percentages use case A as the reference, but they describe three different quantities. A careful public sentence says “In the toy model, lower current reduced calculated cable-heating energy by 43.75%, while energy delivered to the receiver also fell by 13.75%.” That sentence is more useful than “43.75% energy efficiency improvement,” which fails to name a definition or measure equal service. The difference in denominators is the reason seemingly similar percentages cannot be casually compared.

The surprising result: a larger delivered share, less delivered energy

In A, 240 of 384 Wh reaches the receiver, a 62.5% share. In B, 207 of 288 Wh reaches it, a 71.875% share. B therefore has a larger receiver-energy fraction under the chosen model boundary, even though the absolute receiver energy has fallen from 240 Wh to 207 Wh. There is no contradiction: the total source energy also declined. The share increased by 9.375 percentage points, not by 9.375% of A’s fraction. This teaches two lessons. First, a percentage share is not an absolute quantity. Second, a stronger fraction does not establish unchanged useful output. The word “efficiency” must always come with a clearly defined boundary and result, not be used as a free-standing compliment.

Percentage points are not percentage changes

A percentage-point difference subtracts two percentage values directly. Thus 71.875% minus 62.5% equals 9.375 percentage points. If the question asks for a relative percentage increase in the delivered share, the comparison would instead be 9.375 divided by 62.5 multiplied by 100, or 15%. These are different mathematical descriptions of the same pair of percentages. Neither is a 15% increase in delivered energy, because the delivered energy decreased. Many misleading headlines exploit exactly this confusion. In an answer, name whether the result is a share difference, a relative change in share, or a change in absolute energy. A correct operation used for the wrong quantity still gives a wrong conclusion.

Why case B cannot inherit case A’s service

There is no independent evidence about the receiver’s real function, output or user experience in this hypothetical circuit. Lower current at fixed source voltage does not automatically describe a more efficient device doing the same work. Indeed, the calculated receiver energy is 207 Wh rather than 240 Wh. To test equal service, an investigation would need a defined service metric, a controlled comparison and measurements or credible modelling that establish equivalence. For a lamp, for example, electrical energy alone is not a measure of useful lighting; brightness and the relevant duration would matter. The present guide does not model a particular appliance. Its correct lesson is how to recognise a missing condition, not how to claim a device upgrade.

What if the line resistance were changed instead?

Alternative C, studied in the preceding Mathematics volume, stipulated the original current profile while reducing modelled resistance from 2 Ω to 1 Ω. Under that expressly fixed-current assumption, line heating would halve from 144 Wh to 72 Wh. That is a different thought experiment from B. If the electrical circuit were physically altered, current might not remain the same, so a real comparison would need a more complete load model. Students should not combine C’s 50% figure with B’s 43.75% and declare a 93.75% saving. Combining independent factors requires an explicitly defined combined scenario. The exact assumptions should appear immediately beside any comparison table or conclusion.

An honest claim register for a public report

A useful EMS exercise is to classify each statement as acceptable, acceptable only with qualification, or unsupported. “Case A produces 144 Wh of line heating in four hours” is acceptable in the stipulated model. “Case B produces 81 Wh” is also acceptable. “Case B reduces line heating by 43.75%” is acceptable when the baseline and durations are named. “The school will save 43.75% on bills” is unsupported because there is no real bill, tariff or school load data. “The receiver gets the same energy in B” is false under the model because B delivers 207 Wh rather than 240 Wh. “B is safe to install” is wholly unsupported and not a purpose of the exercise. The strongest report is precise enough for each line to be checked.

Do not turn an educational table into electrical instructions

No part of this guide should be followed as a wiring procedure or used to select a cable, fuse, transformer, source or protective device. Actual electrical systems have safety rules, temperature changes, component ratings, alternating-current considerations, installation standards and professional obligations that this model deliberately leaves out. A safe school explanation can use a printed table, a calculator, a teacher-approved simulation and carefully stated assumptions. It should not ask students to connect anything to mains electricity. The distinction matters because an accurate classroom calculation can be dangerously incomplete as practical design advice. The responsible scientific conclusion is narrower than the everyday phrase “the system works.”

The English problem: a sentence may be grammatical but false

Consider the sentence “The revised plan delivers exactly the same output with less waste.” It contains no obvious subject–verb or quantifier error, but the calculated model does not support it. This shows why the preceding English Editing volume and this EMS audit have different jobs. In an exam-style Editing task, correct specified grammatical errors; do not quietly turn the passage into a scientific essay. In a broader writing or communication exercise, test every substantial claim against its evidence. You may need to replace the unsupported sentence with one that says what the table actually demonstrates. Good English does not mean long or impressive language. It means that the reader can understand an accurate statement without guessing its limitations.

Rewrite one headline with minimal distortion

The draft “43.75% less energy used with no loss of performance” has at least two problems. It fails to say which energy is lower, and it promises constant performance without evidence. A more defensible headline is “Changing the Modelled Current Reduces Calculated Cable Heating.” A useful subheading can add that cable heating falls from 144 Wh to 81 Wh over four hours, while receiver energy also falls from 240 Wh to 207 Wh. This is not as dramatic, but it is informative. Notice the exact nouns: modelled current, cable heating, receiver energy. The editor did not need a fancy synonym for “less.” The editor needed to name the relevant quantities and reject an unwarranted causal story.

A reader-safe public paragraph

An example paragraph for a fictional school display is: “In a simplified four-hour energy calculation, reducing the stated current in each period to three-quarters of its original value changes the modelled line-heating energy from 144 Wh to 81 Wh. It also changes the energy supplied by the source from 384 Wh to 288 Wh and the energy delivered to the receiver from 240 Wh to 207 Wh. The example illustrates how electrical heating depends on current and why different percentages require different denominators. It is not a measurement of our school or evidence that a real appliance would provide the same service.” Every sentence has a purpose: conditions, values, comparison, interpretation and boundary. That is clearer than an enthusiastic claim that leaves the reader to infer the missing facts.

Present the numbers in a text-only decision table

The case A totals can be read as source 384 Wh, line heating 144 Wh and receiver 240 Wh. Case B totals are source 288 Wh, line heating 81 Wh and receiver 207 Wh. Differences B minus A are −96 Wh, −63 Wh and −33 Wh. Writing a short textual table in this order helps readers see that all three changes point downward in absolute terms. If a chart is added later, its axis must distinguish source input, line heating and receiver delivery instead of stacking unrelated percentages. For this series, text suffices. The calculations and comparison boundary are more important than a decorative visual. The whole ledger can be reconstructed with the given source voltage, resistance, currents and interval durations.

Check the three types of evidence

A scientific write-up often mixes givens, observations and derived results. In this exercise, “24 V source” and “2 Ω line” are given assumptions. The four-hour current profiles are stipulated inputs. Values such as 144 Wh, 81 Wh and 207 Wh are derived from those inputs. There are no laboratory observations or measurements of a building in the dataset. That distinction should appear in both the Science interpretation and the English report. Writing “we measured 207 Wh at the receiver” would be false because no meter was used. Writing “the model predicts 207 Wh under the given conditions” correctly expresses the status. The verb can make a major difference in whether a reader understands the strength of evidence.

An uncertainty question that the table cannot settle

Suppose a student asks how accurately the school could expect 43.75% less cable heating in a real installation. The honest answer is that our toy model cannot determine that. It assumes constant line resistance, idealised source conditions and stipulated currents. There is no instrument uncertainty, load behaviour, temperature history or real installation data. Assigning an invented ±1% range would only make the claim look scientific. An examination answer may use stated measurement precision and uncertainty when provided, but should not manufacture it. A good evaluation tells the reader which additional observations or parameters are needed. Sometimes “not determinable from the given information” is the strongest defensible answer.

Inspect the result from the other direction

A useful reliability test is to subtract the receiver and line figures from the source. In A, 384 − 240 − 144 = 0 Wh. In B, 288 − 207 − 81 = 0 Wh. That zero difference is expected because the model includes exactly two energy destinations. It is not evidence of zero loss in a real system. The independent calculation checks arithmetic consistency, not external realism. Another check divides B’s 81 Wh loss by A’s 144 Wh, giving 0.5625. That is the square of the current factor 0.75. Each cross-check catches a different category of error: one checks conservation in the ledger, while the other checks the expected scaling relation.

A conflict between true numbers and a false promise

Imagine a committee member insists that the 43.75% figure is true and therefore the headline must be acceptable. You can agree about the arithmetic without agreeing about the headline. The calculation describes line-heating reduction, not school-wide energy use or identical useful output. The appropriate reply is calm and specific: “The 43.75% calculation is correct for line heating. Our model also shows a decrease in energy delivered to the receiver, so we should not claim unchanged service.” This response does not accuse anyone of dishonesty or bury the reader in equations. It identifies where the inference goes beyond the data. That is the practical value of combining subject knowledge with clear communication.

How this connects to Physics assessment

SEAB’s 2027 G3 Physics K323 syllabus assesses scientific understanding, application, analysis and evaluation, and practical scientific skills. The assessment comprises multiple-choice, structured/free-response and practical papers, with weightings of 30%, 50% and 20%. This teaching case revises power relationships, conservation-style energy ledgers, explanatory limits and the interpretation of results. It is not an official practical setup. For an examination question, use the given conditions, choose a relevant equation and explain the physical reason for a result. When evaluating unfamiliar information, distinguish what follows from the data from what would require more evidence. These habits matter whether or not any question resembles this invented example.

How this connects to Mathematics assessment

For 2027 G3 Mathematics K310, SEAB specifies two written papers, each lasting two hours and fifteen minutes and carrying 50% of the subject assessment. Paper 2 ends with a real-world-context question. This learner case offers practice with duration-weighted totals, percentages, ratio factors, equality checks and interpreting mathematical constraints. The main mathematical trap is choosing the wrong denominator or averaging rates without time weights. The second trap is treating a higher proportion as a higher absolute quantity. To answer a decision question, show the result of the correct operation and state whether the compared cases are operating under equivalent conditions. Mathematics rewards a supported conclusion, not a headline that sounds confident.

How this connects to English assessment

For 2027 G3 English Language K300, Paper 1 has Editing, Situational Writing and Continuous Writing sections. Editing tests grammar, while writing demands attention to purpose, audience and coherent language. The preceding volume trained grammatical restraint; this one applies precise sentences to a decision memo. English also matters when interpreting a comprehension passage containing statistics, qualifications and competing claims. A student should be able to identify the asserted conclusion, the evidence offered and the missing condition. In writing, use verbs such as “shows”, “suggests” and “would require” with care. Saying “shows” when the model only assumes a result can overstate evidence. Clear communication grows from knowing what the evidence supports.

A ten-minute evidence-hearing routine

Set aside two minutes to copy the assumptions and identify the three energy boundaries. Spend three minutes recreating the totals for A and B, including 384 = 240 + 144 and 288 = 207 + 81. Use two minutes to calculate absolute changes and the correct relative percentages. During the next two minutes, classify the committee’s draft claims as supported, conditional or unsupported. Reserve the final minute to write a plain-language decision with its limitation. These times are an optional independent practice exercise, not an examination timing instruction. If the learner repeatedly misses a step, give that specific skill more time before trying to accelerate the whole routine.

An independent four-week revision plan

In week one, revise Physics quantities and units: current, potential difference, resistance, power and energy. Rebuild case A using only the written inputs. In week two, add case B and practise time-weighted calculations, absolute differences and percentage denominators. In week three, read short invented claims and classify them, then rewrite unsupported sentences without losing their useful information. In week four, attempt a new three-interval case with no worked solution beside you. Write a short evidence memo and ask someone else to identify the model assumptions from it. Retest a changed scenario several days later. Independence is demonstrated when the reasoning transfers, not when the learner remembers this exact set of numbers.

Parents and tutors: ask for an explanation, not a slogan

Ask the learner: “How can case B have a greater receiver share but deliver less receiver energy?” A secure answer explains that B’s source total is smaller, and that a percentage share must be interpreted with its denominator. Then ask which claim can safely be put in a public notice: “43.75% less modelled cable heating” or “43.75% lower school electricity bills.” The former is conditionally supported; the latter is not. Finally ask the learner to calculate the receiver total of 207 Wh without looking at the answer. These three checks test mathematical understanding, scientific boundaries and precise English at once. A calm follow-up question does more than repeating the numbers aloud.

Independent evidence-hearing questions and worked answers

Attempt each question before revealing its explanation. The purpose is to recognise the quantity asked for, complete a justified calculation, and explain what follows from it. A number without its unit and reference boundary is not a finished decision.

Exercise 1: Reconstruct A’s cable heating

Task: Given currents 2 A, 4 A and 6 A for 1, 2 and 1 h with R=2 Ω, compute the heating energy.

Worked answer: The rates are 8, 32 and 72 W. Their energies are 8, 64 and 72 Wh. Total is 144 Wh. Show the time multiplier in each row to avoid summing rates instead of energy.

Exercise 2: Check A’s source energy

Task: Source voltage is 24 V throughout A. Calculate the source’s four-hour energy.

Worked answer: Source powers 48, 96 and 144 W give 48 + 192 + 144 = 384 Wh. This belongs to the source boundary; it is not receiver energy.

Exercise 3: Check A’s receiver energy

Task: Find receiver energy if the source supplies 384 Wh and the line loses 144 Wh.

Worked answer: Within the two-destination model, receiver energy is 384 − 144 = 240 Wh. The rowwise calculation gives the same answer.

Exercise 4: Calculate B’s heating rows

Task: At currents 1.5, 3 and 4.5 A, each through a 2 Ω line, calculate heating powers.

Worked answer: The rates are 4.5 W, 18 W and 40.5 W. The last is not 45 W: calculate 4.5 squared first, then multiply by two.

Exercise 5: Calculate B’s heating total

Task: Use durations of 1 h, 2 h and 1 h with B’s rates.

Worked answer: 4.5 + 36 + 40.5 = 81 Wh. An equal-weight mean of the three rates would not compute the four-hour energy.

Exercise 6: Find B’s source energy

Task: Use a 24 V source and currents 1.5, 3, 4.5 A over the same intervals.

Worked answer: Source powers 36, 72, 108 W produce 36 + 144 + 108 = 288 Wh. Compare this with A’s 384 Wh before making a cost claim.

Exercise 7: Find B’s receiver energy

Task: Subtract B’s line heating from its source energy.

Worked answer: 288 − 81 = 207 Wh. The receiver received 33 Wh less than A’s 240 Wh, so identical energy delivery is false under this model.

Exercise 8: Find the line-loss change

Task: How much lower is line-heating energy in B than A?

Worked answer: 144 − 81 = 63 Wh. This is an absolute reduction in modelled line heating, not a reduction in total electrical energy.

Exercise 9: Write the percentage reduction

Task: What percentage of A’s line-heating energy is removed in B?

Worked answer: 63/144 × 100 = 43.75%. State the original baseline as denominator and the four-hour line-heating boundary.

Exercise 10: Compare the source energy

Task: What is the source-energy reduction from A to B in percentage terms?

Worked answer: (384 − 288)/384 × 100 = 25%. The number differs from 43.75% because it measures a different quantity.

Exercise 11: Compare the receiver energy

Task: Calculate the percentage fall in delivered receiver energy.

Worked answer: (240 − 207)/240 × 100 = 13.75%. This directly contradicts a promise of unchanged delivery in the toy model.

Exercise 12: Calculate A’s receiver share

Task: What portion of source energy reaches the receiver in A?

Worked answer: 240/384 = 62.5%. This is a modelled fraction for one boundary, not evidence of whole-grid or appliance efficiency.

Exercise 13: Calculate B’s receiver share

Task: What portion of source energy reaches the receiver in B?

Worked answer: 207/288 = 71.875%. Even a larger share can correspond to smaller delivered energy when the source total also falls.

Exercise 14: Find percentage points

Task: How much greater is B’s receiver share than A’s?

Worked answer: 71.875% − 62.5% = 9.375 percentage points. Do not describe that direct subtraction as a 9.375% relative increase.

Exercise 15: Find relative share change

Task: What is the relative change in receiver-energy share?

Worked answer: 9.375/62.5 × 100 = 15%. This compares two proportions; delivered energy itself falls, so the distinction must be stated.

Exercise 16: Audit a headline

Task: “Case B provides the same energy with 43.75% less loss.” Accept or reject?

Worked answer: Reject the equal-energy claim. The 43.75% refers only to lower cable heating; B’s receiver energy is 207 Wh rather than 240 Wh.

Exercise 17: Audit a cost claim

Task: “This proves lower school utility bills.” Accept or reject?

Worked answer: Reject. There are no school measurements, tariffs, or actual appliance outputs. A fictional low-voltage model cannot determine a real bill.

Exercise 18: Audit a scientific verb

Task: Does “we measured 81 Wh” describe the evidence correctly?

Worked answer: No. The values are calculated from stated assumptions, not measured. Replace with “the model gives 81 Wh under the stated conditions.”

Exercise 19: Check an accounting identity

Task: A student writes 288 Wh source, 207 Wh receiver and 91 Wh line loss for B. What fails?

Worked answer: 207 + 91 = 298, not 288. The account is inconsistent. The correctly calculated line heating is 81 Wh, restoring the 288 Wh total.

Exercise 20: Apply a current scale factor

Task: Why does 0.75 of each current yield 56.25% of the original heating?

Worked answer: With fixed R and durations, line power is proportional to I². Squaring 0.75 gives 0.5625; the remaining fraction is 56.25% and the reduction is 43.75%.

Exercise 21: Differentiate equality and fairness

Task: If both cases last four hours, is the comparison necessarily a same-service comparison?

Worked answer: No. Equal time does not ensure equal receiver output. This is only a comparison of calculated totals under different stipulated currents.

Exercise 22: Write an honest two-sentence conclusion

Task: Summarise the gain and trade-off clearly.

Worked answer: B reduces modelled four-hour cable heating by 63 Wh, or 43.75%, relative to A. Under the same fixed-source model it also delivers 33 Wh less energy to the receiver, so equivalent service is not established.

Frequently asked questions

Is EMS an official SEC examination paper?

No. EMS is an integrated English, Mathematics and Science learning approach. The 2027 G3 subjects have separate syllabus codes and assessment requirements.

What is the most important error in the draft headline?

It confuses a reduction in line heating with unchanged useful delivery. The receiver energy falls from 240 Wh to 207 Wh in this model.

Does B use 43.75% less source energy?

No. B’s source energy is 288 Wh instead of 384 Wh, which is 25% lower relative to A.

Why is line-heating energy 81 Wh in B?

The stipulated currents are 0.75 of the original values. Squaring that factor makes the heating energy 0.5625 of 144 Wh, or 81 Wh.

Is the receiver share higher in B?

Yes: 71.875% versus 62.5% for A. But B delivers fewer watt-hours in total.

Does a higher energy share always mean better real-world performance?

No. The model does not define the useful service or account for all real components. A higher fraction alone is not a guarantee.

What are the verified 2027 G3 SEC subject codes?

English K300, Mathematics K310 and Physics K323. Check SEAB for the student’s exact syllabus and candidature.

Are the figures drawn from a real school?

No. They are entirely fictional teaching values. The calculations should never be presented as measured school results.

Can students use the guide to work on electrical cables?

No. The model is for mathematical and scientific reasoning only and gives no installation, equipment-selection or electrical safety advice.

How should a questionable percentage be checked?

Name its numerator, denominator, measured or modelled quantity, time period and comparison conditions.

What is the simplest independent check?

Verify that source energy equals receiver energy plus line heating in both A and B: 384 = 240 + 144 and 288 = 207 + 81.

How should an English Editing question be treated?

Correct grammatical errors as asked. A separate evidence audit may correct unsupported scientific claims, but should not be confused with the grammar section.

What belongs in the conclusion of an evaluation?

A directly supported result, the comparison boundary, a necessary qualification and, where relevant, what evidence is still missing.

How can a parent test genuine understanding?

Ask the learner why B’s receiver percentage rises while its delivered energy falls, and request a worked explanation rather than only a number.

Official references and connected learning routes

SEAB’s current subject documents control examination details. This independent learning case is not an official examination question and EMS is not an additional examinable SEC subject.

Small Group Tutorials

How to Perform in the new G3 SEC Examinations | Learner’s Guide Vol 0736 | EMS Variable-Load Decision — Test Cable Losses, Useful Delivery and Public Claims

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