A DC motor has flux = constant and armature current = 20 A.
1. Torque is directly proportional to armature current under constant flux condition.
2. If current doubles, torque also doubles.
3. Torque is independent of flux.
4. Torque depends on product of flux and current.
Which of the above statements is/are correct?
Answer & step-by-step solution
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current. If flux is held constant, torque varies directly with armature current, so doubling current ideally doubles torque. Key relation: T=kΦI_a.
Exam focus: Constant flux converts the general torque equation into T∝I_a. Common trap: Do not generalize constant-flux behavior into 'torque is independent of flux'.
Statement-wise Verification
- Statement 1 - Correct.
Torque is directly proportional to armature current under constant flux condition.
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current. - Statement 2 - Correct.
If current doubles, torque also doubles.
If flux is held constant, torque varies directly with armature current, so doubling current ideally doubles torque. - Statement 3 - Incorrect.
Torque is independent of flux.
The correct principle is: Constant flux converts the general torque equation into T∝I_a. - Statement 4 - Correct.
Torque depends on product of flux and current.
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current.
Core Concept
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current. If flux is held constant, torque varies directly with armature current, so doubling current ideally doubles torque. The flux term cannot be omitted in the general torque equation.
Formula / Key Relationship
T=kΦI_a.
Why the Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.
Exam Shortcut / Approach
Constant flux converts the general torque equation into T∝I_a.
Common Mistake
Do not generalize constant-flux behavior into 'torque is independent of flux'.
Quick Revision
DC Motor Torque and Armature Current is linked with Torque Equation, DC Motors and Electrical Machines. Constant flux converts the general torque equation into T∝I_a.
एक DC मोटर में फ्लक्स = स्थिर और आर्मेचर करंट = 20 A है।
1. स्थिर फ्लक्स की स्थिति में टॉर्क आर्मेचर करंट के समानुपाती होता है।
2. यदि करंट दोगुना हो, तो टॉर्क भी दोगुना होता है।
3. टॉर्क फ्लक्स से स्वतंत्र है।
4. टॉर्क फ्लक्स और करंट के गुणनफल पर निर्भर करता है।
उपरोक्त में से कौन-सा/से कथन सही है/हैं?
उत्तर और चरणबद्ध हल
DC मोटर का विद्युतचुंबकीय टॉर्क एयर-गैप फ्लक्स और आर्मेचर करंट के गुणनफल के समानुपाती है। स्थिर फ्लक्स पर टॉर्क आर्मेचर करंट के साथ सीधे बदलता है, इसलिए करंट दोगुना करने पर टॉर्क दोगुना होता है। मुख्य संबंध: T=kΦI_a।
परीक्षा फोकस: स्थिर फ्लक्स पर T∝I_a। सामान्य गलती: इसे 'टॉर्क फ्लक्स से स्वतंत्र' मान लेना।
विस्तृत हल (मूल भाषा में)
Statement-wise Verification
- Statement 1 - Correct.
Torque is directly proportional to armature current under constant flux condition.
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current. - Statement 2 - Correct.
If current doubles, torque also doubles.
If flux is held constant, torque varies directly with armature current, so doubling current ideally doubles torque. - Statement 3 - Incorrect.
Torque is independent of flux.
The correct principle is: Constant flux converts the general torque equation into T∝I_a. - Statement 4 - Correct.
Torque depends on product of flux and current.
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current.
Core Concept
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current. If flux is held constant, torque varies directly with armature current, so doubling current ideally doubles torque. The flux term cannot be omitted in the general torque equation.
Formula / Key Relationship
T=kΦI_a.
Why the Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.
Exam Shortcut / Approach
Constant flux converts the general torque equation into T∝I_a.
Common Mistake
Do not generalize constant-flux behavior into 'torque is independent of flux'.
Quick Revision
DC Motor Torque and Armature Current is linked with Torque Equation, DC Motors and Electrical Machines. Constant flux converts the general torque equation into T∝I_a.
એક DC મોટરમાં ફ્લક્સ = અચળ અને આર્મેચર કરંટ = 20 A છે.
1. અચળ ફ્લક્સની સ્થિતિમાં ટોર્ક આર્મેચર કરંટના સમપ્રમાણમાં હોય છે.
2. જો કરંટ બમણો થાય, તો ટોર્ક પણ બમણો થાય છે.
3. ટોર્ક ફ્લક્સથી સ્વતંત્ર છે.
4. ટોર્ક ફ્લક્સ અને કરંટના ગુણાકાર પર આધાર રાખે છે.
ઉપરોક્તમાંથી કયું/કયા વિધાન સાચું/સાચા છે?
જવાબ અને પગલાવાર ઉકેલ
DC મોટરનો વિદ્યુતચુંબકીય ટોર્ક એર-ગેપ ફ્લક્સ અને આર્મેચર કરંટના ગુણાકારના સમપ્રમાણમાં છે. અચળ ફ્લક્સ પર ટોર્ક આર્મેચર કરંટ સાથે સીધો બદલાય છે, તેથી કરંટ બમણો કરતાં ટોર્ક બમણો થાય છે. મુખ્ય સંબંધ: T=kΦI_a.
પરીક્ષા મુદ્દો: અચળ ફ્લક્સ પર T∝I_a. સામાન્ય ભૂલ: તેને 'ટોર્ક ફ્લક્સથી સ્વતંત્ર' માની લેવું.
વિગતવાર ઉકેલ (મૂળ ભાષામાં)
Statement-wise Verification
- Statement 1 - Correct.
Torque is directly proportional to armature current under constant flux condition.
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current. - Statement 2 - Correct.
If current doubles, torque also doubles.
If flux is held constant, torque varies directly with armature current, so doubling current ideally doubles torque. - Statement 3 - Incorrect.
Torque is independent of flux.
The correct principle is: Constant flux converts the general torque equation into T∝I_a. - Statement 4 - Correct.
Torque depends on product of flux and current.
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current.
Core Concept
The electromagnetic torque of a DC motor is proportional to the product of air-gap flux and armature current. If flux is held constant, torque varies directly with armature current, so doubling current ideally doubles torque. The flux term cannot be omitted in the general torque equation.
Formula / Key Relationship
T=kΦI_a.
Why the Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.
Exam Shortcut / Approach
Constant flux converts the general torque equation into T∝I_a.
Common Mistake
Do not generalize constant-flux behavior into 'torque is independent of flux'.
Quick Revision
DC Motor Torque and Armature Current is linked with Torque Equation, DC Motors and Electrical Machines. Constant flux converts the general torque equation into T∝I_a.
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