1
JEE Main 2017 (Offline)
MCQ (Single Correct Answer)
+4
-1
A magnetic needle of magnetic moment 6.7 $$\times$$ 10-2 A m2 and moment of inertia 7.5 $$\times$$ 10-6 kg m2 is performing simple harmonic oscillations in a magnetic field of 0.01 T. Time taken for 10 complete oscillations is:
A
8.76 s
B
6.65 s
C
8.89 s
D
6.98 s
2
JEE Main 2016 (Online) 10th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
A fighter plane of length 20 m, wing span (distance from tip of one wing to the tip of the other wing) of 15 m and height 5 m is flying towards east over Delhi. Its speed is 240 ms−1. The earth’s magnetic field over Delhi is 5 $$\times$$10−5 T with the declination angle ~ 0o and dip of $$\theta$$ such that sin $$\theta$$ = 2/3 . If the voltage developed is VB between the lower and upper side of the plane and VW between the tips of the wings then VB and VW are close to :
A
VB = 45 mV; VW = 120 mV with right side of pilot at higher voltage
B
VB = 45 mV; VW = 120 mV with left side of pilot at higher voltage
C
VB = 40 mV; VW = 135 mV with right side of pilot at high voltage
D
VB = 40 mV; VW = 135 mV with left side of pilot at higher voltage
3
JEE Main 2016 (Offline)
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Hysteresis loops for two magnetic materials $$A$$ and $$B$$ are given below :

These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use :

A
$$A$$ for transformers and $$B$$ for electric generators.
B
$$B$$ for electromagnets and transformers.
C
$$A$$ for electric generators and transformers.
D
$$A$$ for electromagnets and $$B$$ for electric generators.
4
JEE Main 2014 (Offline)
MCQ (Single Correct Answer)
+4
-1
The coercivity of a small magnet where the ferromagnet gets demagnetized is $$3 \times {10^3}\,A{m^{ - 1}}.$$ The current required to be passed in a solenoid of length $$10$$ $$cm$$ and number of turns $$100,$$ so that the magnet gets demagnetized when inside the solenoid, is :
A
$$30$$ $$mA$$
B
$$60$$ $$mA$$
C
$$3$$ $$A$$
D
$$6A$$
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