How does induced emf in DC motor react to supply voltage?
Answer & step-by-step solution
The induced armature emf in a running DC motor is the back emf. By Lenz's law it opposes the applied supply voltage, limiting armature current as the motor gains speed.
Concept & Reasoning
When the armature of a DC motor rotates in the magnetic field, an emf is induced in its conductors. The direction of that induced emf is governed by Lenz's law: it opposes the cause producing it. Since the supply causes the armature to rotate, the induced emf acts opposite to the supply and is therefore called back emf. The armature circuit is commonly written V = Eb + IaRa (neglecting brush drop). At starting Eb = 0, which explains the high starting current; as speed rises, Eb rises and current falls.
How to Solve It in the Exam
Motor induced emf = back emf = opposes supply.
Important Exam Point
Use the armature-voltage equation to connect back emf with starting-current behavior.
Quick Trick
Motor induced emf = back emf = opposes supply.
Common Mistake
Do not confuse motor back emf with generator emf polarity; both follow electromagnetic induction but circuit roles differ.
DC मोटर में प्रेरित emf सप्लाई वोल्टेज के प्रति कैसी प्रतिक्रिया करता है?
उत्तर और चरणबद्ध हल
चलती DC मोटर में प्रेरित आर्मेचर emf बैक emf है। लेन्ज़ के नियम से यह लागू सप्लाई वोल्टेज का विरोध करता है और गति बढ़ने पर आर्मेचर करंट सीमित करता है।
विस्तृत हल (मूल भाषा में)
Concept & Reasoning
When the armature of a DC motor rotates in the magnetic field, an emf is induced in its conductors. The direction of that induced emf is governed by Lenz's law: it opposes the cause producing it. Since the supply causes the armature to rotate, the induced emf acts opposite to the supply and is therefore called back emf. The armature circuit is commonly written V = Eb + IaRa (neglecting brush drop). At starting Eb = 0, which explains the high starting current; as speed rises, Eb rises and current falls.
How to Solve It in the Exam
Motor induced emf = back emf = opposes supply.
Important Exam Point
Use the armature-voltage equation to connect back emf with starting-current behavior.
Quick Trick
Motor induced emf = back emf = opposes supply.
Common Mistake
Do not confuse motor back emf with generator emf polarity; both follow electromagnetic induction but circuit roles differ.
DC મોટરમાં પ્રેરિત emf સપ્લાય વોલ્ટેજ પ્રત્યે કેવી રીતે વર્તે છે?
જવાબ અને પગલાવાર ઉકેલ
ચાલતી DC મોટરમાં પ્રેરિત આર્મેચર emf એ બેક emf છે. લેન્ઝના નિયમ મુજબ તે લાગુ સપ્લાય વોલ્ટેજનો વિરોધ કરે છે અને ઝડપ વધતાં આર્મેચર કરંટ મર્યાદિત કરે છે.
વિગતવાર ઉકેલ (મૂળ ભાષામાં)
Concept & Reasoning
When the armature of a DC motor rotates in the magnetic field, an emf is induced in its conductors. The direction of that induced emf is governed by Lenz's law: it opposes the cause producing it. Since the supply causes the armature to rotate, the induced emf acts opposite to the supply and is therefore called back emf. The armature circuit is commonly written V = Eb + IaRa (neglecting brush drop). At starting Eb = 0, which explains the high starting current; as speed rises, Eb rises and current falls.
How to Solve It in the Exam
Motor induced emf = back emf = opposes supply.
Important Exam Point
Use the armature-voltage equation to connect back emf with starting-current behavior.
Quick Trick
Motor induced emf = back emf = opposes supply.
Common Mistake
Do not confuse motor back emf with generator emf polarity; both follow electromagnetic induction but circuit roles differ.
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