Under IEC drawing practice both are a plain rectangle sitting in a wire, and mistaking one for the other means misreading what the circuit is protected by.
Look for a line running through the rectangle lengthwise: that is a fuse. A bare rectangle is an IEC resistor. If the diagram uses North American conventions the question does not arise, because its resistors are drawn as zigzags instead — so identify the convention first, then read the component.
The IEC rectangle form of the resistor and the fuse symbol are both plain rectangles in a wire, separated only by the fuse's additional line.
Drawn from the visual attributes recorded for each symbol. Only traits the two records disagree about are listed.
| Trait | Resistor symbol | Fuse symbol |
|---|---|---|
| Built from | lines and dots, squares | squares, lines and dots |
| Resistor symbol | Fuse symbol | |
|---|---|---|
| What it does | Opposes current continuously, by design | Carries current until an overload melts it open |
| How to tell them apart | Plain rectangle, or a zigzag in North American practice | Rectangle with a line through it lengthwise |
| Is it meant to fail? | No — a failed resistor is a fault | Yes — failing open is the whole purpose |
| Why they look alike | IEC 60617 draws passive components as plain rectangles | Shares that rectangle, distinguished only by the added line |
| Relationship (from Symbolwise's records) | Commonly confused with Fuse symbol — The IEC rectangle form of the resistor and the fuse symbol are both plain rectangles in a wire, separated only by the fuse's additional line. | Commonly confused with Resistor symbol — Under IEC practice the resistor is also a plain rectangle in a wire; the fuse's internal line is the distinguishing mark. |
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.
Alpha is a Greek letter and stands for a quantity — an angle, a coefficient, a significance level. The proportionality sign is an operator and stands between two quantities to say they keep a constant ratio. The drawings differ in that the proportionality sign's right-hand stroke runs out in an open curve rather than closing into the letter's tail.
Look at the left-hand edge. A straight flat back is an AND gate: the output is true only when every input is. A curved concave back is an OR gate: true when any input is. Everything else about the shapes is similar, which is why the back edge is worth checking deliberately rather than at a glance.
Equal-length lines mean a capacitor. Alternating long and short lines mean a battery, with the long line positive. If the second line is curved rather than straight it is a polarised capacitor — still a capacitor, but one that must be fitted the right way round.
Look at the pattern. Even short dashes throughout is a hidden line: an edge that exists but is concealed behind material. Long dashes alternating with dots is a centre line: an axis of symmetry or the centre of a circle, which is not a physical edge at all. Reading a centre line as an edge is the commonest beginner's error on a drawing.