RRB JE 2019 Exam: Physics Quiz [Electricity & Magnetism] | 28th January

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Q1.Safety fuse wire used in domestic electrical appliances is made of metal of low
घरेलू विद्युत उपकरणों में उपयोग की जाने वाली सुरक्षा फ्यूज तार कम_____ धातु से बना होता है
(a) resistance/ प्रतिरोध
(b) melting point/ गलनांक
(c) specific gravity/ विशिष्ट गुरुत्व
(d) conductance/ प्रवाहकत्त्व

Sol. A fuse wire is a single, small gauge made up of a tin coated copper wire material of low melting point, usually contained in a carrier of some sort, providing a weak point in an electrical circuit that will melt on overload and disconnect the electricity load. An alloy of lead and tin coated wire is used as the material of the fuse wire.

Q2. If input frequency of a full wave rectifier be n, then output frequency would be 
यदि एक पूर्ण तरंग रेक्टिफायर की इनपुट आवृत्ति n है, तो उत्पादित आवृत्ति कितनी होगी?
(a) n/2
(b) n
(c) 3n/2
(d) 2n

Sol. Frequency is measured by how frequently the period is completed in one second.A Time period (denoted by ‘T’ ) is the time needed for one complete cycle of vibration to pass in a given point. The output signal completes a period twice as fast as the input frequency.

Q3.A transformer works on the principle of
एक ट्रांसफार्मर किसके सिद्धांत पर कार्य करता है
(a) self induction/ स्वत: प्रेरण
(b) mutual induction/ आपसी प्रेरण
(c) generator /जनरेटर
(d) inverter/इन्वर्टर

Sol. A transformer consists of two electrically isolated coils and operates on Faraday’s principal of “mutual induction”, in which an EMF is induced in the transformers secondary coil by the magnetic flux generated by the voltages and currents flowing in the primary coil winding.

Q4. In AC circuits, AC meters measure
AC सर्किट में, AC मीटर क्या मापता है?
(a) mean values/ औसत आंकड़े
(b) rms values/ आरएमएस मान
(c) peak values/ पीक मान
(d) mean square values/ माध्य वर्ग मान

Sol. In AC circuits, AC meters measure rms values.

Q5.The angle between the magnetic meridian and the geographical meridian and the geographical meridian        at a place is 
एक जगह पर चुंबकीय मेरिडियन और भौगोलिक मेरिडियन के बीच का कोण ______ है?
(a) Dip/डीप
(b) Declination/ डीक्लिनेशन
(c) Latitude/ अक्षांश
(d) Azimuth/ दिगंश

Sol. The vertical plane that passes through the true geographical North and South (or geographical axis of Earth) is known as the geographical meridian. The angle between the magnetic meridian and the geographic meridian at a place is called declination at that place.

Q6.A compass needle cannot be used to detect 
एक कंपास की सुई का उपयोग क्या पता लगाने के लिए नहीं किया जा सकता है?
(a) Magnetic North-South direction/ चुंबकीय उत्तर-दक्षिण दिशा
(b) Polarity of a magnet/ एक चुंबक की ध्रुवीयता
(c) Strength of a magnet/ एक चुंबक की शक्ति
(d) Direction of magnetic field/चुम्बकिय क्षेत्र की दिशा

Sol. A compass needle cannot be used to detect Strength of a magnet.

Q7. Indicate the false statement about the resistance of a wire
तार के प्रतिरोध के बारे में इनमें से कौन सा कथन गलत है?
(a) It depend on material of wire/ यह तार के सामग्री पर निर्भर करता है
(b) It is unrectly proportional to the length of wire/ यह स्वतंत्र रूप से तार की लंबाई के साथ आनुपातिक है
(c) It is directly proportional to the area of cross-section of wire/ यह तार के क्रॉस-सेक्शन के क्षेत्रफल से सीधे आनुपातिक है
(d) Resistance of metallic wire increases with increase in temperature / तापमान में वृद्धि के साथ धातु के तार का प्रतिरोध बढ़ता है

Sol. The resistance of a current carrying conductor is inversely proportional to the area of cross section of the conductor. The reason is because the resistance occurs due to the collision of electrons/charged particles.So resistance is inversely proportional to area of cross section of the conductor.

Q8.For which of the following substances, the resistance decreases with increase in temperature?
निम्नलिखित पदार्थों में से किसके तापमान में वृद्धि के साथ प्रतिरोध कम हो जाता है?
(a) Pure silicon/ शुद्ध सिलिकॉन
(b) Copper/ तांबा
(c) Nichrome/ निक्रोम
(d) Platinum/ प्लैटिनम

Sol. Pure Silicon at room temperature has perhaps one conduction electron for every 1013 (that’s ten trillion) atoms. Increasing the temperature of intrinsic semiconductors provides more thermal energy for electrons to absorb, and thus will increase the number of conduction electrons. Voila – decreased resistance.

Q9. The ratio of intensity of magnetisation to the magnetisation force is known as 
               चुंबकत्व की तीव्रता का चुंबकत्व बल से अनुपात किस रूप में जाना जाता है?
(a) flux density / फ्लक्स घनत्व
(b) susceptibility / संवेदनशीलता
(c) relative permeability / तुलनात्मक भेद्दता
(d) none of the above/इनमें से कोई नहीं

Sol. In electromagnetism, the magnetic susceptibility is one measure of the magnetic properties of a material. The susceptibility indicates whether a material is attracted into or repelled out of a magnetic field.

Q10.  When a bar magnet is cut into two equal halves, the pole strength of each piece
जब एक बार चुंबक दो बराबर हिस्सों में काटा जाता है, तो प्रत्येक टुकड़े की ध्रुव शक्ति
(a) Becomes double/दुगनी हो जाती है
(b) Becomes half/आधी हो जाती है
(c) Becomes zero/शून्य हो जाती है
(d) Remains the same/समान रहती है

Sol. When a bar magnet is cut into two equal halves, the pole strength of each piece Remains the same.

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