---
title: "Desirable properties of heating elements"
subject: "Utilization of Electrical Energy"
chapter: 5
key: "semester_7/utilization_of_electrical_energy:properties-heating-elements"
source: https://www.bctengineer.com/q/semester_7/utilization_of_electrical_energy/properties-heating-elements
site: BCT Engineering
---

# Desirable properties of heating elements

Utilization of Electrical Energy · Chapter 5: Electric Heating

- Asked in: 2081 Bhadra, 3 marks; 2079 Baisakh, 3 marks (asked 2 times)
- Video: [LECTURE   15   Characteristic of good heating elements & Cause of Failure of Element](https://www.youtube.com/watch?v=u-pYlSVAKWg) — Bha_Win
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/utilization_of_electrical_energy/properties-heating-elements
- Whole chapter: https://www.bctengineer.com/md/semester_7/utilization_of_electrical_energy/chapter-5

## Question

What are the desirable properties of heating elements?

## Short answer

Desirable heating element properties: high resistivity (compact), high melting point, low temperature coefficient (stable power), oxidation resistance at high temperature, mechanical strength and ductility for winding, low cost. Common materials: nichrome (up to 1150°C), Kanthal (up to 1300°C), silicon carbide (up to 1450°C), molybdenum/tungsten (above 1500°C in vacuum/inert gas).

## Answer

A heating element converts electrical energy into heat by $I^2R$ loss, so its material must withstand high temperature for a long time. The desirable properties are:

1. **High resistivity:** a short length of wire gives the required resistance, so the element is compact.
2. **High melting point:** it can work at high temperature with a safety margin.
3. **Low temperature coefficient of resistance:** resistance (and so power) stays nearly constant from cold to hot.
4. **Free from oxidation at high temperature:** oxidation reduces cross-section and causes early burnout.
5. **High mechanical strength and ductility:** it can be drawn into wire or strip and wound into coils, and it does not break when heated and cooled repeatedly.
6. **Low cost and easy availability.**

**Common materials:** nichrome (80% Ni, 20% Cr, up to about 1150°C), Kanthal (Fe-Cr-Al, up to about 1300°C), silicon carbide (up to about 1450°C), molybdenum and tungsten (in vacuum or inert gas, above 1500°C).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why should a heating element material have high resistivity?
   A. So it conducts heat away well
   B. So a short length gives the required resistance and the element is compact
   C. So it needs less current at any power
   D. So it oxidises slowly
   Answer: B. High resistivity allows the needed resistance from a short length of wire. (Key point: High resistivity)

2. Why is a low temperature coefficient of resistance desirable?
   A. It lowers the melting point
   B. Resistance and power stay nearly constant from cold to hot
   C. It increases oxidation resistance
   D. It makes the wire ductile
   Answer: B. With little change of resistance with temperature, the power stays nearly constant. (Key point: Low temperature coefficient)

3. What happens if the element oxidises at high temperature?
   A. Resistivity rises and the wire cools
   B. Cross-section reduces, causing early burnout
   C. The melting point increases
   D. Ductility improves
   Answer: B. Oxidation eats away the cross-section, so the element burns out early. (Key point: Oxidation resistance)

## Related in Utilization of Electrical Energy

- [Nichrome wire size for 4.5 kW resistance oven](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Anichrome-oven-4-5kw-wire-size) — Utilization of Electrical Energy, chapter 5, asked 3×
- [Nichrome wire size for 5.5 kW resistance oven](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Anichrome-oven-5-5kw-wire-size) — Utilization of Electrical Energy, chapter 5, asked 2×
- [Nichrome strip width for 40 kW 3-phase oven](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Anichrome-strip-40kw-oven-width) — Utilization of Electrical Energy, chapter 5, asked 2×
- [Nichrome strip width for 30 kW 3-phase oven](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Anichrome-strip-30kw-oven-width) — Utilization of Electrical Energy, chapter 5, asked 2×

## Related in other subjects

- [Desirable properties of subgrade soil](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asubgrade-properties) — Transportation Engineering I, chapter 6, asked 11×
- [Desirable properties of road aggregates](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aaggregate-desirable-properties) — Transportation Engineering I, chapter 6, asked 5×
- [Desirable properties of bituminous mixes](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Abituminous-mix-desirable-properties) — Transportation Engineering I, chapter 6, asked 3×
- [Desirable properties of bitumen](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Abitumen-desirable-properties) — Transportation Engineering I, chapter 6