आधारभूत विद्युत् (Basic Electrical) – Basic Electrical Engineering MCQ

आधारभूत विद्युत् (Basic Electrical): प्रश्न र उत्तर

सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।

सही: ० / ०

641. A DC shunt generator fails to build up voltage if:

     कits residual magnetism is very strong खit is run above rated speed गits load is disconnected घits field circuit resistance exceeds the critical field resistance
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

642. A starter is needed for a DC motor mainly because:

     कthe motor cannot start without a capacitor खit reverses the direction of rotation गit supplies the field with AC घthe back emf is zero at standstill, so the starting current would be very large
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

643. A DC shunt motor is preferred where:

     कnearly constant speed is needed with varying load खvery high starting torque is the main need गthe speed must vary widely with load घthe motor must run on AC as well
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

644. Before magnetic saturation, the torque of a DC series motor is proportional to:

     कthe armature current खthe square of the armature current गthe square root of the armature current घthe supply frequency
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

645. The speed of a DC shunt motor can be raised above its rated speed by:

     कinserting resistance in the armature circuit खincreasing the field current गreducing the field current (field weakening) घreducing the supply voltage
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

646. The direction of rotation of a DC shunt motor can be reversed by:

     कreversing the supply polarity खreversing the armature and the field connections together गreversing either the armature connections or the field connections, but not both घincreasing the field resistance
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

647. An isolation transformer with a 1 : 1 turns ratio is used mainly to:

     कstep up the voltage खchange the frequency गconvert AC into DC घelectrically separate equipment from the supply for safety
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

648. In an ideal transformer on load, the primary and secondary windings have equal:

     कampere-turns खcurrents गvoltages घnumbers of turns
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

649. The no-load primary current of a transformer:

     कis equal to the full-load current खis small and lags the voltage by nearly 90° गis in phase with the voltage घleads the voltage by nearly 90°
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।

650. Transformers are rated in kVA rather than kW because:

     कthey cannot supply real power खtheir losses depend on voltage and current, not on the load power factor गtheir efficiency is always 100% घthe kW rating would always be larger
     💬 टिप्पणी / गल्ती रिपोर्ट (०)

     छलफल / प्रश्न उत्तरमा गल्ती छ

     पठाउनुहोस्

     टिप्पणी जाँचपछि मात्र देखिन्छ।