1
COMEDK 2025 Afternoon Shift
MCQ (Single Correct Answer)
+1
-0
When a dielectric slab of dielectric constant $\mathrm{k}=2$ is used to fill the space between the plates of a parallel plate capacitor, the capacitance of the capacitor is found to be $20 \mu \mathrm{~F}$. What will be the capacitance when the slab is replaced with air?
A
$10 \mu F$
B
$40 \mu F$
C
$20 \mu F$
D
$5 \mu F$
2
COMEDK 2025 Afternoon Shift
MCQ (Single Correct Answer)
+1
-0
de Broglie wave length associated with an electron accelerated through a potential difference ' V ' is ' $\lambda$ '. If the accelerating potential is halved, what will be the new wave length associated with the charged particle?
A
$\frac{\lambda}{\sqrt{2}}$
B
$\frac{\lambda}{2}$
C
$2 \lambda$
D
$\sqrt{2} \boldsymbol{\lambda}$
3
COMEDK 2025 Afternoon Shift
MCQ (Single Correct Answer)
+1
-0
An open pipe is in second harmonic with frequency $f_1$. One end of the tube is closed and frequency is increased to $f_2$ and it resonates again with nth harmonic. For what value of n , the ratio of $\frac{f_1}{f_2}$ is $\frac{4}{5}$ ?
A
3
B
9
C
5
D
7
4
COMEDK 2025 Afternoon Shift
MCQ (Single Correct Answer)
+1
-0
Across the 220 V source of internal resistance $20 \Omega$, how many lamps of $40 \mathrm{~W}, 100 \mathrm{~V}$ can be connected in parallel so that all the lamps may glow with full brightness.
A
40
B
15
C
30
D
20
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