1
COMEDK 2024 Evening Shift
MCQ (Single Correct Answer)
+1
-0

A transformer of $$100 \%$$ efficiency has 200 turns in the primary and 40000 turns in the secondary. It is connected to a $$220 \mathrm{~V}$$ main supply and secondary feeds to a $$100 \mathrm{~K} \Omega$$ resistance. The potential difference per turn is

A
11 V
B
18 V
C
25 V
D
1.1 V
2
COMEDK 2024 Evening Shift
MCQ (Single Correct Answer)
+1
-0

The current in a coil changes steadily from $$3 \mathrm{~A}$$ to $$5 \mathrm{~A}$$ in $$0.2 \mathrm{~s}$$ when an emf of $$2 \mu \mathrm{V}$$ is induced in it. The self-inductance of the coil is

A
0.2 mH
B
20 $$\mu H$$
C
2 $$\mu H$$
D
0.2 $$\mu H$$
3
COMEDK 2024 Evening Shift
MCQ (Single Correct Answer)
+1
-0

The magnetic flux linked with a coil is given by the equation: $$\phi=8 t^2+t+10$$. The e.m.f. induced in the coil in the $$3^{\text {rd }}$$ second will be

A
49 V
B
33 V
C
16 V
D
20 V
4
COMEDK 2024 Afternoon Shift
MCQ (Single Correct Answer)
+1
-0

A wire ' 1 ' $$\mathrm{cm}$$ long bent into a circular loop is placed perpendicular to the magnetic field of flux density '$$B^{\prime} W b \mathrm{~m}^{-2}$$. Within $$0.1 \mathrm{sec}$$, the loop is changed into a square of side '$$a$$' $$\mathrm{cm}$$ and flux density is doubled. The value of e.m.f. induced is

A
$$ \frac{-5 B\left(8 л \mathrm{a}^2-\mathrm{l}^2\right)}{2} $$
B
$$ \frac{5 B\left(8 л a^2-l^2\right)}{2 л} $$
C
$$ \frac{-5 B\left(8 л a^2-l^2\right)}{2 л} $$
D
$$ \frac{-5 B\left(8 a^2-l^2\right)}{2 \pi} $$
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