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Class 12 Physics
Electromagnetic Induction
Quiz 1
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The coupling co-efficient of the perfectly coupled coils is:
0%
Zero
0%
1
0%
slightly more than 1
0%
infinite
Explanation
1
1 henry is equal to :
0%
\(\frac{weber}{ampere}\)
0%
\(\frac{weber}{Volt}\)
0%
weber ampere
0%
None of these
Explanation
\(\frac{weber}{ampere}\)
The magnetic field is parallel to a surface, then the magnetic flux through the surface is :
0%
zero
0%
small but not zero
0%
infinite
0%
large but not infinite
Explanation
small but not zero
In the expression e = -\(\frac{d∅}{dt}\), the -ve sign signifies:
0%
The induced emf is produced only when magnetic flux decreases
0%
The induced emf opposes the change in the magnetic flux
0%
The induced emf is opposite to the direction of the flux
0%
None of these
Explanation
The induced emf opposes the change in the magnetic flux
An e
-
and a p
-
are moving parallel to each other in a magnetic field. The magnetic force acting on the p
+
is:
0%
1840 times that on e
-
0%
less than that of e
-
0%
same as that of e
-
0%
slightly more than that of e
-
Explanation
same as that of e
-
Which of the following is not equal to a henry?
0%
\(\frac{Volt second}{ampere}\)
0%
\(\frac{Volt second^2}{Coulomb}\)
0%
\(\frac{Volt^2 second}{Coulomb}\)
0%
\(\frac{Jole second}{Coulomb^2}\)
Explanation
\(\frac{Volt^2 second}{Coulomb}\)
A transformer is used to light 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A. Then the efficiency of the transformer is:
0%
11%
0%
50%
0%
80%
0%
90%
Explanation
90%
The magnetic flux (∅) linked with a coil is related to the number of turns (N) ofthe coil as:
0%
f ∝ N
0%
f ∝ N
-1
0%
f ∝ N
2
0%
f ∝ N
-2
Explanation
f ∝ N
The magnetic flux (∅) lined with a coil is related to its area (s) as:
0%
∅ ∝ s
0%
∅ ∝ s²
0%
∅ ∝ s
1/2
0%
∅ ∝ s
-1/2
Explanation
∅ ∝ s
If the magnetic flux linked with a coil through which a current off ampere is set up is ∅, then the coefficient of self-inductance of the coil is:
0%
\(\frac{l}{∅}\)
0%
\(\frac{∅}{l}\)
0%
∅l
0%
None of these
Explanation
\(\frac{∅}{l}\)
In a uniform magnetic field B, a wire in the form of a semicircle of radius r rotated about the diameter of the circle with angular frequency ‘ω’. The axis of rotation is perpendicular to the field. If the total resistance of the circuit is R the mean power generated per period of rotation is :
0%
\(\frac{Bπr^2ω}{2R}\)
0%
\(\frac{(Bπr^2ω)^2}{8R}\)
0%
\(\frac{(Bπrω)^2}{2R}\)
0%
\(\frac{(Bπrω^2)^2}{8R}\)
Explanation
\(\frac{(Bπr^2ω)^2}{8R}\)
The role of inductance is equivalent to:
0%
inertia
0%
force
0%
energy
0%
momentum
Explanation
inertia
A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 rad s
-1
. If the horizontal component of earth's magnetism is 2 × 10
-5
T, then e.m.f. developed between the two ends of the conductor is:
0%
5 µV
0%
50 µV
0%
5 mV
0%
50 mV
Explanation
5 µV
coil of L = 8.4 mH and R = 6 Ω is connected to a 12 V battery. The current in the coil is 1.0 A at approx'time of:
0%
500 s
0%
20 s
0%
35 ms
0%
1 ms
Explanation
1 ms
If I current is flowing inductance L, then the dimension of \(\frac{3}{2}\) LI² is equivalent to:
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charge
0%
force
0%
momentum
0%
energy
Explanation
momentum
The phase difference between the flux linkage and the emf in a rotating coil in a uniform magnetic field is:
0%
zero
0%
\(\frac{π}{2}\)
0%
\(\frac{π}{4}\)
0%
π
Explanation
\(\frac{π}{4}\)
A choke is used as a resistance in :
0%
dc circuits
0%
ac circuits
0%
both ac and dc circuits
0%
neither (a) nor (b)
Explanation
ac circuits
The SI unit of magnetic flux is:
0%
T
0%
Tn
-2
0%
Wb
0%
Wb m
-2
Explanation
Wb
For purely capacitive circuits, power factor is:
0%
0
0%
-1
0%
1
0%
infinity
Explanation
0
The magnetic flux linked with a coil is inversely proportional to the?
0%
magnetic field
0%
area of cross section
0%
number of turns
0%
none of these
Explanation
magnetic field
0 h : 0 m : 1 s
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