What is an electric circuit and how does it function in the context of IB MYP Science?

An electric circuit is a closed loop that allows electric current to flow through it, powered by a voltage source like a battery. In the IB MYP Science curriculum, students learn that circuits consist of components such as resistors, capacitors, and switches, which control the flow of electricity. Understanding electric circuits is fundamental to studying electromagnetism, as it helps explain how electrical energy is transferred and used in various devices.

How do series and parallel circuits differ in terms of current and voltage?

In a series circuit, components are connected end-to-end, so the same current flows through each component, but the voltage is divided among them. In contrast, a parallel circuit has components connected across the same two points, so each component receives the full voltage, but the current is divided among the branches. This distinction is crucial in the IB MYP Science curriculum for understanding how different circuit configurations affect the performance of electrical devices.

What role do resistors play in an electric circuit, and why are they important in electromagnetism?

Resistors are components that limit the flow of electric current in a circuit, providing resistance measured in ohms. They are essential for controlling the current and protecting sensitive components from damage due to excessive current. In electromagnetism, resistors help in managing energy distribution and are used in various applications, such as voltage regulation and signal processing, which are key concepts in the IB MYP Science curriculum.

How does Ohm's Law apply to electric circuits, and why is it significant in the study of electromagnetism?

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance. This relationship is expressed as V = IR, where V is voltage, I is current, and R is resistance. Ohm's Law is significant in electromagnetism as it helps predict how changes in voltage or resistance affect current flow, a fundamental concept in the IB MYP Science curriculum for analyzing and designing circuits.

What safety precautions should be taken when working with electric circuits in a science lab setting?

When working with electric circuits in a science lab, it is important to follow safety precautions to prevent accidents. These include ensuring all equipment is properly insulated, using low-voltage power sources, never touching live wires, and wearing protective gear like gloves and goggles. Understanding these safety measures is crucial in the IB MYP Science curriculum to ensure safe and effective learning experiences while exploring electromagnetism and electric circuits.

Why is "Adding parallel resistances directly instead of using 1/R formulae." a common mistake in Electric Circuits?

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 is "Assuming current is the same in every branch of a parallel circuit." a common mistake in Electric Circuits?

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 is "Drawing a battery the same as a cell." a common mistake in Electric Circuits?

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.

ElectromagnetismIB MYP Sciences (Years 1-5)

Electric Circuits

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Electric Circuits — IB MYP Sciences: series, parallel, circuit symbols and electrical power

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.

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Recognise and draw the standard circuit symbols.
MYP Sciences A — State the current and voltage rules for series and parallel circuits.
MYP Sciences C — Calculate total resistance, current and voltage in series and parallel circuits.
MYP Sciences C — Use P = VI and E = Pt to find power and energy.
MYP Sciences D — Evaluate why household wiring uses parallel rather than series circuits.

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:

A handful of standard symbols you'll need most often in MYP Sciences.

Memorise the cell (long line = +), lamp, resistor, ammeter and voltmeter at minimum.

Cell symbol: long line = +, short thick line = −.
Lamp: circle with X.
Resistor: rectangle. Variable: rectangle with diagonal arrow.
Ammeter: circle with A. Voltmeter: circle with V.

Series circuits

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.

Current is the same at every point in the loop: $I_1 = I_2 = I_{\text{total}}$ .
Voltage is shared between components: $V_{\text{total}} = V_1 + V_2$ .
Resistance adds: $R_{\text{total}} = R_1 + R_2$ .

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.

Series: one loop, one path for current.
I is the same everywhere. V is shared. R adds.
Failure of one component breaks the whole circuit.

Parallel circuits

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.

Voltage is the same across each branch: $V_1 = V_2 = V_{\text{supply}}$ .
Current divides between branches: $I_{\text{total}} = I_1 + I_2$ .
Resistance: $\frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2}$ . Total resistance is less than the smallest individual resistance.

Households use parallel wiring so each appliance gets the full mains voltage and can be switched on or off independently of the others.

Parallel: multiple branches.
V is the same across each branch. Currents add. R combines into a smaller total.
Failure of one branch doesn't affect the others.

Electrical power

P = V × I tells you the energy transferred per second.

Electrical power is the rate of energy transfer:

$P = V \times I$

Combining with Ohm's law gives two more forms:

$P = I^2 R \quad \text{and} \quad P = \frac{V^2}{R}$

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.

P = VI = I²R = V²/R. Unit watt (W) = J/s.
Energy = Pt. Unit joule (J).
1 kWh = 1 000 W × 3 600 s = 3.6 × 10⁶ J (the unit on household electricity bills).

How it’s examined

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.

Master this Topic

Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.

Take this whole topic with you

Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Electric Circuits, ready to print or save as PDF.

Step-by-step worked examples — Electric Circuits

Step-by-step solutions to past-paper-style questions on electric circuits, written exactly the way a tutor would explain them at the board.

1Series resistance
Getting started• series
Question
Three resistors of 4 Ω, 6 Ω and 10 Ω are connected in series. Find the total resistance.
Step-by-step solution
1. Step 1
  In series, resistances add.
  $R = 4 + 6 + 10$
2. Step 2
  R = 20 Ω.
Answer
20 Ω.
2Parallel resistance
Building confidence• parallel
Question
Two 6 Ω resistors are connected in parallel. Find the total resistance.
Step-by-step solution
1. Step 1
  1/R = 1/6 + 1/6 = 2/6 = 1/3.
2. Step 2
  R = 3 Ω (smaller than 6 Ω, as expected for parallel).
Answer
3 Ω.
3Current and voltage in series
Building confidence• series, Ohm's law
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
1. Step 1
  Total R = 5 + 15 = 20 Ω.
2. Step 2
  Current I = V/R = 12/20 = 0.60 A (same through both).
3. Step 3
  V across 5 Ω = IR = 0.60 × 5 = 3.0 V.
4. 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.
4Power and energy of an appliance
Stretch• power, energy
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
1. Step 1
  Current I = P/V = 1 200 / 240 = 5.0 A.
2. Step 2
  Time = 2 × 60 = 120 s.
3. Step 3
  Energy E = Pt = 1 200 × 120 = 144 000 J = 144 kJ.
Answer
(a) 5.0 A. (b) 144 kJ.

Key Formulae — Electric Circuits

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.

Series resistance
$R = R₁ + R₂ + ...$
When to use
When all components sit in one loop.
Parallel resistance
$1/R = 1/R₁ + 1/R₂ + ...$
When to use
When components are on separate branches.
Electrical power
$P = V × I$
$P$
power (W)
$V$
voltage (V)
$I$
current (A)
When to use
Rate of energy transfer in any circuit element. Can also be written I²R or V²/R.
Electrical energy
$E = P × t$
$E$
energy transferred (J)
$P$
power (W)
$t$
time (s)
When to use
Total energy used by an appliance over a time period.

Key Definitions and Keywords — Electric Circuits

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.

Series circuit
Examiner keyword
A circuit where all components sit in one loop, so the same current flows through each.
Parallel circuit
Examiner keyword
A circuit with two or more branches, each carrying part of the total current. The voltage across each branch is the same.
Circuit symbols
Standard internationally-agreed symbols for components (cell, lamp, resistor, switch, ammeter, voltmeter).
Electrical power
Examiner keyword
The rate of electrical energy transfer in a component. P = VI. Unit watt (W) = J/s.
Electrical energy
Energy transferred by an electric current. E = Pt. Unit joule (J).
Kilowatt-hour (kWh)
Energy unit used on electricity bills. 1 kWh = 1 000 W × 3 600 s = 3.6 × 10⁶ J.

Common Mistakes and Misconceptions — Electric Circuits

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.

✕Adding parallel resistances directly instead of using 1/R formulae.
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.
✕Assuming current is the same in every branch of a parallel circuit.
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.
✕Drawing a battery the same as a cell.
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.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Electric Circuits — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

ElectromagnetismIB MYP Sciences (Years 1-5)

Electric Circuits

Work through the notes, try the practice questions, then take the quiz. The report tells you exactly what to revise next.

Previous Next

Learn this Topic

Start with the slides for the quick version, then go deeper with the full study notes.

Short Study Notes in the form of Slides

Read the notes first. If the method in a worked example clicks, you're ready for the questions.

Short Study Notes — Electric Circuits

Start with these resources to cover the key concepts, then work through the practice questions.

Page 1 / 0

Detailed Notes

Full prose, callouts and a recap — built for A* mastery, not just a quick scan.

Take these study notes with you

Download a branded PDF — full prose, callouts, recap and memorise list for Electric Circuits, ready to print or save offline.

Electric Circuits — IB MYP Sciences: series, parallel, circuit symbols and electrical power

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Recognise and draw the standard circuit symbols.
MYP Sciences A — State the current and voltage rules for series and parallel circuits.
MYP Sciences C — Calculate total resistance, current and voltage in series and parallel circuits.
MYP Sciences C — Use P = VI and E = Pt to find power and energy.
MYP Sciences D — Evaluate why household wiring uses parallel rather than series circuits.

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:

A handful of standard symbols you'll need most often in MYP Sciences.

Memorise the cell (long line = +), lamp, resistor, ammeter and voltmeter at minimum.

Cell symbol: long line = +, short thick line = −.
Lamp: circle with X.
Resistor: rectangle. Variable: rectangle with diagonal arrow.
Ammeter: circle with A. Voltmeter: circle with V.

Series circuits

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.

Current is the same at every point in the loop: $I_1 = I_2 = I_{\text{total}}$ .
Voltage is shared between components: $V_{\text{total}} = V_1 + V_2$ .
Resistance adds: $R_{\text{total}} = R_1 + R_2$ .

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.

Series: one loop, one path for current.
I is the same everywhere. V is shared. R adds.
Failure of one component breaks the whole circuit.

Parallel circuits

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.

Voltage is the same across each branch: $V_1 = V_2 = V_{\text{supply}}$ .
Current divides between branches: $I_{\text{total}} = I_1 + I_2$ .
Resistance: $\frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2}$ . Total resistance is less than the smallest individual resistance.

Households use parallel wiring so each appliance gets the full mains voltage and can be switched on or off independently of the others.

Parallel: multiple branches.
V is the same across each branch. Currents add. R combines into a smaller total.
Failure of one branch doesn't affect the others.

Electrical power

P = V × I tells you the energy transferred per second.

Electrical power is the rate of energy transfer:

$P = V \times I$

Combining with Ohm's law gives two more forms:

$P = I^2 R \quad \text{and} \quad P = \frac{V^2}{R}$

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.

P = VI = I²R = V²/R. Unit watt (W) = J/s.
Energy = Pt. Unit joule (J).
1 kWh = 1 000 W × 3 600 s = 3.6 × 10⁶ J (the unit on household electricity bills).

How it’s examined

Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.

Master this Topic

Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.

Take this whole topic with you

Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Electric Circuits, ready to print or save as PDF.

Step-by-step worked examples — Electric Circuits

Step-by-step solutions to past-paper-style questions on electric circuits, written exactly the way a tutor would explain them at the board.

1Series resistance
Getting started• series
Question
Three resistors of 4 Ω, 6 Ω and 10 Ω are connected in series. Find the total resistance.
Step-by-step solution
1. Step 1
  In series, resistances add.
  $R = 4 + 6 + 10$
2. Step 2
  R = 20 Ω.
Answer
20 Ω.
2Parallel resistance
Building confidence• parallel
Question
Two 6 Ω resistors are connected in parallel. Find the total resistance.
Step-by-step solution
1. Step 1
  1/R = 1/6 + 1/6 = 2/6 = 1/3.
2. Step 2
  R = 3 Ω (smaller than 6 Ω, as expected for parallel).
Answer
3 Ω.
3Current and voltage in series
Building confidence• series, Ohm's law
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
1. Step 1
  Total R = 5 + 15 = 20 Ω.
2. Step 2
  Current I = V/R = 12/20 = 0.60 A (same through both).
3. Step 3
  V across 5 Ω = IR = 0.60 × 5 = 3.0 V.
4. 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.
4Power and energy of an appliance
Stretch• power, energy
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
1. Step 1
  Current I = P/V = 1 200 / 240 = 5.0 A.
2. Step 2
  Time = 2 × 60 = 120 s.
3. Step 3
  Energy E = Pt = 1 200 × 120 = 144 000 J = 144 kJ.
Answer
(a) 5.0 A. (b) 144 kJ.

Key Formulae — Electric Circuits

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.

Series resistance
$R = R₁ + R₂ + ...$
When to use
When all components sit in one loop.
Parallel resistance
$1/R = 1/R₁ + 1/R₂ + ...$
When to use
When components are on separate branches.
Electrical power
$P = V × I$
$P$
power (W)
$V$
voltage (V)
$I$
current (A)
When to use
Rate of energy transfer in any circuit element. Can also be written I²R or V²/R.
Electrical energy
$E = P × t$
$E$
energy transferred (J)
$P$
power (W)
$t$
time (s)
When to use
Total energy used by an appliance over a time period.

Key Definitions and Keywords — Electric Circuits

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.

Series circuit
Examiner keyword
A circuit where all components sit in one loop, so the same current flows through each.
Parallel circuit
Examiner keyword
A circuit with two or more branches, each carrying part of the total current. The voltage across each branch is the same.
Circuit symbols
Standard internationally-agreed symbols for components (cell, lamp, resistor, switch, ammeter, voltmeter).
Electrical power
Examiner keyword
The rate of electrical energy transfer in a component. P = VI. Unit watt (W) = J/s.
Electrical energy
Energy transferred by an electric current. E = Pt. Unit joule (J).
Kilowatt-hour (kWh)
Energy unit used on electricity bills. 1 kWh = 1 000 W × 3 600 s = 3.6 × 10⁶ J.

Common Mistakes and Misconceptions — Electric Circuits

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.

✕Adding parallel resistances directly instead of using 1/R formulae.
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.
✕Assuming current is the same in every branch of a parallel circuit.
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.
✕Drawing a battery the same as a cell.
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.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Electric Circuits — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

Electric Circuits

Short Study Notes in the form of Slides

Short Study Notes — Electric Circuits

Detailed Notes

What you’ll learn

How it’s examined

1Series resistance

2Parallel resistance

3Current and voltage in series

4Power and energy of an appliance

Series resistance

Parallel resistance

Electrical power

Electrical energy

Series circuit

Parallel circuit

Circuit symbols

Electrical power

Electrical energy

Kilowatt-hour (kWh)

✕Adding parallel resistances directly instead of using 1/R formulae.

✕Assuming current is the same in every branch of a parallel circuit.

✕Drawing a battery the same as a cell.

Practice questions

Past paper style quiz

Assess your understanding

Electric Circuits — frequently asked questions

Electric Circuits

Short Study Notes in the form of Slides

Short Study Notes — Electric Circuits

Detailed Notes

What you’ll learn

How it’s examined

1Series resistance

2Parallel resistance

3Current and voltage in series

4Power and energy of an appliance

Series resistance

Parallel resistance

Electrical power

Electrical energy

Series circuit

Parallel circuit

Circuit symbols

Electrical power

Electrical energy

Kilowatt-hour (kWh)

✕Adding parallel resistances directly instead of using 1/R formulae.

✕Assuming current is the same in every branch of a parallel circuit.

✕Drawing a battery the same as a cell.

Practice questions

Past paper style quiz

Assess your understanding

Electric Circuits — frequently asked questions