GATE EE 2018 Set 1 — Question 62
Go beyond PYQs with Success TrackerAI-powered personalised practice and doubt support. Unlimited practice on eligible plans; AI usage limits apply.NAT+2 / -0MediumGenerator & Motor CharacteristicsDC MachinesElectrical Machines
Electrical Machines → DC Machines → Generator & Motor Characteristics
Last updated
Question
A 200 V DC series motor, when operating from rated voltage while driving a certain load, draws 10 A current and runs at 1000 r.p.m. The total series resistance is 1 . The magnetic circuit is assumed to be linear. At the same supply voltage, the load torque is increased by 44%. The speed of the motor in r.p.m. (rounded to the nearest integer) is ________ .
Correct answer
823 to 827
Solution
Given:
Supply voltage
Initial armature current
Initial speed
Total series resistance Step 1: Calculate initial back EMF ()
Step 2: Determine the relationship between torque and current
For a DC series motor with a linear magnetic circuit, flux .
Torque .Step 3: Calculate new armature current ()
Given that the load torque is increased by 44%, .
Step 4: Calculate new back EMF ()
Step 5: Calculate new speed ()
We know .
Rounding to the nearest integer, the speed is 825 r.p.m.
Supply voltage
Initial armature current
Initial speed
Total series resistance Step 1: Calculate initial back EMF ()
Step 2: Determine the relationship between torque and current
For a DC series motor with a linear magnetic circuit, flux .
Torque .Step 3: Calculate new armature current ()
Given that the load torque is increased by 44%, .
Step 4: Calculate new back EMF ()
Step 5: Calculate new speed ()
We know .
Rounding to the nearest integer, the speed is 825 r.p.m.
Continue learning with Success Tracker
A step still unclear? Work through it with support
Use Success Tracker to ask about the reasoning, then try another GATE EE question to check your understanding.
AI-powered practice· Unlimited practice on eligible plans
- PYQs with solutions
- Attempt available previous-year questions, then compare your reasoning with the worked solution. Coverage varies by stream.
- Practice that adapts
- Choose a topic, work on weaker areas and bookmark questions to revisit. Your attempts feed your progress tracking.
- AI doubt support
- Ask follow-up questions about a step or concept while practising, instead of stopping at the final answer.
Unlimited practice is available on eligible plans. Free practice and AI usage have limits; check the current plan allowances before choosing.
This page stays readable without an account. AI responses can be wrong; check them against the solution and source material.
More questions on DC Machines
2026 Set 1 Q17A 15 kVA, 1100 V/220 V, single-phase two-winding transformer is configured as a 1.32 kV/1.1 kV…2026 Set 1 Q20A certain application requires power at a frequency of , while the available grid…2026 Set 1 Q21Which one of the following options is correct regarding the typical double-squirrel-cage structure…2026 Set 1 Q22The figure shows the single-line diagram of a synchronous generator delivering …2026 Set 1 Q31A 220V/12V single-phase transformer is designed for use in India and rated 100 VA at 50 Hz. Later,…