1
WB JEE 2018
MCQ (Single Correct Answer)
+2
-0.5
Change Language
The bob of a pendulum of mass m, suspended by an inextensible string of length L as shown in the figure carries a small charge q. An infinite horizontal plane conductor with uniform surface charge density $$\sigma$$ is placed below it. What will be the time period of the pendulum for small amplitude oscillations?

WB JEE 2018 Physics - Electrostatics Question 21 English
A
$$2\pi \sqrt {{L \over {\left( {g - {{mq} \over {{\varepsilon _0}\sigma }}} \right)}}} $$
B
$$\sqrt {{L \over {\left( {g - {{mq\sigma } \over {{\varepsilon _0}}}} \right)}}} $$
C
$${1 \over {2\pi }}\sqrt {{L \over {\left( {g - {{q\sigma } \over {{\varepsilon _0}m}}} \right)}}} $$
D
$$2\pi \sqrt {{L \over {\left( {g - {{q\sigma } \over {{\varepsilon _0}m}}} \right)}}} $$
2
WB JEE 2018
MCQ (More than One Correct Answer)
+2
-0
Change Language
A non-zero current passes through the galvanometer G shown in the circuit when the key K is closed and its value does not change when the key is opened. Then, which of the following statement(s) is/are true?

WB JEE 2018 Physics - Current Electricity Question 21 English
A
the galvanometer resistance is infinite.
B
the current through the galvanometer is 40 mA.
C
After the key is closed, the current through the 200$$\Omega$$ resistor is same as the current through the 300$$\Omega$$ resister.
D
The galvanometer resistance is 150$$\Omega$$
3
WB JEE 2018
MCQ (More than One Correct Answer)
+2
-0
Change Language
WB JEE 2018 Physics - Geometrical Optics Question 11 English
A ray of light is incident on a right angled isosceles prism parallel to its base as shown in the figure. Refractive index of the material of the prism is $$\sqrt 2 $$. Then, which of the following statement(s) is/are true?
A
The reflection at P is total internal.
B
The reflection at Q is total internal.
C
The ray emerging at R is parallel to the ray incident at S.
D
Total deviation of the ray is 150$$^\circ$$.
4
WB JEE 2018
MCQ (More than One Correct Answer)
+2
-0
Change Language
The intensity of a sound appears to an observer to be periodic. Which of the following can be the cause of it?
A
The intensity of the source is periodic
B
The source is moving towards the observer
C
The observer is moving away from the source
D
The source is producing a sound composed of two nearby frequencies
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