1
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A proton is moving with a uniform velocity of $${{{10}^6}}$$ ms$$-$$1 along the Y-axis, under the joint action of a magnetic field along Z-axis and an electric field of magnitude 2 $$ \times $$ 104 Vm$$-$$1 along the negative X-axis. If the electric field is switched off, the proton starts moving in a circle. The radius of the circle is nearly (given : $${e \over m}$$ ratio for proton $$ \approx $$ 108 Ckg$$-$$1)
A
0.5 m
B
0.2 m
C
0.1 m
D
0.05 m
2
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
When the frequency of the AC voltage applied to a series LCR circuit is gradually increased from a low value, the impedance of the circuit
A
monotonically increases
B
first increases and then decreases
C
first decreases and then increases
D
monotonically decreases
3
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Six wires, each of resistance r, are connected so as to form a tetrahedron. The equivalent resistance of the combination when current enters through one corner and leaves through some other corner is
A
r
B
2r
C
$${r \over 3}$$
D
$${r \over 2}$$
4
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Consider the circuit shown in the figure.

WB JEE 2017 Physics - Current Electricity Question 18 English
The value of the resistance X for which the thermal power generated in it is practically independent of small variation of its resistance is
A
X = R
B
X = $${R \over 3}$$
C
X = $${R \over 2}$$
D
X = 2R
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