1
COMEDK 2023 Morning Shift
MCQ (Single Correct Answer)
+1
-0

With what velocity should an observer approach a stationary sound source, so that the apparent frequency of sound should appear double the actual frequency?

A
$$v / 2$$
B
$$3 v$$
C
$$2 v$$
D
$$v$$
2
COMEDK 2023 Morning Shift
MCQ (Single Correct Answer)
+1
-0

A dielectric of dielectric constant $$K$$ is introduced such that half of its area of a capacitor of capacitance $$C$$ is occupied by it. The new capacity is

A
$$2 C$$
B
$$\frac{C}{2}$$
C
$$\frac{(1+K) C}{2}$$
D
$$2 C(1+K)$$
3
COMEDK 2023 Morning Shift
MCQ (Single Correct Answer)
+1
-0

Two very long straight parallel wires carry currents $$i$$ and $$2 i$$ in opposite directions. The distance between the wires is $$r$$. At a certain instant of time a point charge $$q$$ is at. a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity $$v$$ is perpendicular to this plane. The magnitude of the force due to the magnetic field acting on the charge at this instant is

A
zero
B
$$\frac{3 \mu_0}{2 \pi} \frac{i q v}{r}$$
C
$$\frac{\mu_0}{\pi} \frac{i q v}{r}$$
D
$$\frac{\mu_0}{2 \pi} \frac{i q v}{r}$$
4
COMEDK 2023 Morning Shift
MCQ (Single Correct Answer)
+1
-0

The magnetic flux linked with a coil satisfies the relation $$\phi=\left(4 t^2+6 t+9\right) \mathrm{Wb}$$, where $$t$$ is time in second. The emf induced in the coil at $$t=2 \mathrm{~s}$$ is

A
22 V
B
18 V
C
16 V
D
40 V
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