Circuit symbols
Scientists use the same agreed symbols worldwide for circuit components.
A circuit diagram replaces realistic drawings with neat symbols. The most common ones in MYP:
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Detailed notes on Electromagnetism for IB MYP Science, covering key concepts, explanations, examples, and exam-focused revision points.
The things students keep getting wrong in this sub-topic, answered.
Drawing a circuit diagram is how you explain electricity in pictures. This MYP Sciences note covers the standard symbols, the difference between series and parallel circuits, current and voltage rules in each, and how to calculate electrical power.
Mapped to the IB MYP Sciences subject guide (2026 onwards).
Scientists use the same agreed symbols worldwide for circuit components.
A circuit diagram replaces realistic drawings with neat symbols. The most common ones in MYP:
One loop. Same current everywhere. Voltage shared between components.
In a series circuit all components are in a single loop. Removing any one breaks the circuit.
Multiple branches. Same voltage across each. Currents add.
In a parallel circuit components sit on separate branches that all connect to the same two end points.
P = V × I tells you the energy transferred per second.
Electrical power is the rate of energy transfer:
Combining with Ohm's law gives two more forms:
Verbatim phrases and definitions MYP criterion-A markschemes credit.
Criterion A typically tests circuit symbols and the series-vs-parallel rules. Criterion C presents a circuit and asks for total resistance, current, voltage or power. Higher-difficulty items combine series and parallel sections.
Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.
Step-by-step solutions to past-paper-style questions on electric circuits, written exactly the way a tutor would explain them at the board.
Question
Three resistors of 4 Ω, 6 Ω and 10 Ω are connected in series. Find the total resistance.
Step-by-step solution
Step 1
In series, resistances add.
Step 2
R = 20 Ω.
Answer
20 Ω.
Question
Two 6 Ω resistors are connected in parallel. Find the total resistance.
Step-by-step solution
Step 1
1/R = 1/6 + 1/6 = 2/6 = 1/3.
Step 2
R = 3 Ω (smaller than 6 Ω, as expected for parallel).
Answer
3 Ω.
Question
Two resistors, 5 Ω and 15 Ω, are connected in series across a 12 V battery. Find (a) the current in the circuit and (b) the voltage across each resistor.
Step-by-step solution
Step 1
Total R = 5 + 15 = 20 Ω.
Step 2
Current I = V/R = 12/20 = 0.60 A (same through both).
Step 3
V across 5 Ω = IR = 0.60 × 5 = 3.0 V.
Step 4
V across 15 Ω = IR = 0.60 × 15 = 9.0 V. Check: 3.0 + 9.0 = 12 V ✓
Answer
(a) 0.60 A. (b) 3.0 V across the 5 Ω, 9.0 V across the 15 Ω.
Question
A 1 200 W kettle is plugged into a 240 V mains supply. Find (a) the current it draws and (b) the energy it transfers in 2 minutes.
Step-by-step solution
Step 1
Current I = P/V = 1 200 / 240 = 5.0 A.
Step 2
Time = 2 × 60 = 120 s.
Step 3
Energy E = Pt = 1 200 × 120 = 144 000 J = 144 kJ.
Answer
(a) 5.0 A. (b) 144 kJ.
The formulae you need to memorise for electric circuits on the IB MYP Sciences paper, with every variable defined in plain English and a note on when to use it.
When to use
When all components sit in one loop.
Definitions to memorise and the exact keywords mark schemes credit for electric circuits answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.
A circuit where all components sit in one loop, so the same current flows through each.
A circuit with two or more branches, each carrying part of the total current. The voltage across each branch is the same.
Standard internationally-agreed symbols for components (cell, lamp, resistor, switch, ammeter, voltmeter).
The rate of electrical energy transfer in a component. P = VI. Unit watt (W) = J/s.
Energy transferred by an electric current. E = Pt. Unit joule (J).
Energy unit used on electricity bills. 1 kWh = 1 000 W × 3 600 s = 3.6 × 10⁶ J.
The traps other students keep falling into on electric circuits questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.
Why it happens
Series adds, so students apply the same to parallel.
How to avoid it
For parallel use 1/R = 1/R₁ + 1/R₂. The total resistance is always SMALLER than the smallest individual resistor — a quick sanity check.
Why it happens
Confusing the series rule with parallel.
How to avoid it
In SERIES, current is the same. In PARALLEL, VOLTAGE is the same — currents in branches depend on each branch's resistance.
Why it happens
A battery 'just looks like more cells'.
How to avoid it
A battery is two or more cells joined — draw multiple cell symbols in line, not just one.
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Memorise the cell (long line = +), lamp, resistor, ammeter and voltmeter at minimum.
Christmas-tree lights of the old style are series-wired: if one bulb fails, the whole string goes out. Modern strings are wired differently to avoid this.
Households use parallel wiring so each appliance gets the full mains voltage and can be switched on or off independently of the others.
Unit: watt (W). 1 W = 1 J/s.
A 60 W lamp running on 230 V mains draws I = P/V = 60 / 230 ≈ 0.26 A. Over 5 minutes (300 s) it transfers E = Pt = 60 × 300 = 18 000 J = 18 kJ of energy.
When to use
When components are on separate branches.
When to use
Rate of energy transfer in any circuit element. Can also be written I²R or V²/R.
When to use
Total energy used by an appliance over a time period.