---
title: "True/False: ampere conductors and temperature rise"
subject: "Electric Machine Design"
chapter: 5
key: "semester_5/electric_machine_design:tf-ampere-conductor-temperature"
source: https://www.bctengineer.com/q/semester_5/electric_machine_design/tf-ampere-conductor-temperature
site: BCT Engineering
---

# True/False: ampere conductors and temperature rise

Electric Machine Design · Chapter 5: DC Machine Design

- Asked in: 2069 Asar, 1+3 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/electric_machine_design/tf-ampere-conductor-temperature
- Whole chapter: https://www.bctengineer.com/md/semester_5/electric_machine_design/chapter-5

## Question

State and justify whether the following statement is TRUE or FALSE: Higher value of ampere conductor in DC machine is higher temperature rise.

## Short answer

TRUE. Higher specific electric loading increases copper loss per unit cooling surface, so temperature rise increases unless cooling is improved.

## Answer

**TRUE.**

Specific electric loading $ac = I_zZ/(\pi D)$ is the ampere-conductors per metre of armature periphery. A higher $ac$ means more conductors (or more current) per unit surface of the armature, so the $I^2R$ copper loss per unit cooling surface increases. Since this heat must be removed through the same surface, the temperature rise increases. That is why $ac$ is limited by the cooling arrangement and the class of insulation, and machines with better ventilation (high-speed or forced cooled) can use a higher $ac$.

**Example:** if $ac$ is raised from 20000 to 30000 A/m with the same conductor current density, the copper volume per metre of periphery rises by 50%, so copper loss per unit surface (and roughly the temperature rise) also rises by about 50%. Typical values are 15000–50000 A/m.

## Check yourself

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

1. Higher ampere conductor in a dc machine gives higher temperature rise. Which is correct?
   A. False: it reduces copper loss
   B. False: it only affects iron loss
   C. True: more I^2R loss per unit cooling surface
   D. True: it increases iron loss
   Answer: C. Heat must leave through the same armature surface. (Key point: True or false)

2. If ac rises from 20000 to 30000 A/m at same current density, copper loss per unit surface rises by about
   A. 10%
   B. 100%
   C. No change
   D. 50%
   Answer: D. Copper volume per unit periphery rises by 1.5 times. (Key point: Example)

3. Which machines can use higher ac?
   A. Slow, enclosed machines
   B. High-speed or forced-ventilated machines
   C. High-voltage machines
   D. Machines with thicker insulation
   Answer: B. Better cooling removes more heat. (Key point: Better cooling)

## Related in Electric Machine Design

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