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Published on: 26/08/2019
Electromagnetic Induction and Alternating Currents
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Questions + Answers key
Take MCQ Physics Test
1.
Does change in magnetic flux induce e.m.f. or current ?
2.
A coil intercepts a magnetic flux of \(0.2\times { 10 }^{ -2 }\) Wb in 0.1 s. What is the emf induced in the coil ?
3.
What is the relation between weber and Maxwell ?
4.
What is the dimensional formula of magnetic flux ?
5.
When is the magnetic flux crossing a given surface area held in a magnetic field maximum?
6.
A transformer is an electric device used for
producing direct current
producing alternating current
changing d.c. into a.c.
changing a.c. voltages
7.
In which of the following appliances, Fleming's right hand rule for direction of induced current is not applicable?
a.c.generator
d.c.generator
induction motor
transformer
8.
The frequency of a.c. generated depends on
speed of rotation of coil
amplitude of a.c
size of coil
all the above
9.
Q factor of resonance is given by
\(\frac { 1 }{ R } \sqrt { \frac { L }{ C } } \)
\(\frac { 1 }{ R } \sqrt { \frac { C }{ L } } \)
\(\frac { 1 }{ L } \sqrt { \frac { R }{ C } } \)
\(\frac { 1 }{ C } \sqrt { \frac { L }{ R } } \)
10.
The resistance of a coil for direct current is 10ohm. When a.c. is sent through the same coil, its resistance would be
10\(\omega\)
> 10ohm
< 10ohm
cannot say
11.
Which of the following does not have the dimension of time?
RC
\(\frac { L }{ R } \)
\(\frac { R }{ L } \)
\(\sqrt { LC } \)
12.
A wire of length 2m moves with a speed of 5m/s perpendicular to a magnetic field of induction 0.1 Wb/m2. The e.m.f. induced in the wire is
1 V
10 V
5 V
2 V
13.
Which one is not an application of eddy currents?
Magnetic brakes
speedometers
Induction furnace
Transformers
14.
The cause of induced e.m.f. is
magnetic flux
magnetic field
area
change in magnetic flux
15.
In the relation \(\phi \) = BA cos \(\theta \), \(\theta \) is angle........
which normal to surface area makes with the direction of magnetic field
which magnetic field makes with the surface
which is never constant
none of the above
1.
Due to change in magnetic flux, e.m.f. is always induced, but induced current will flow only when tghe circuit is complete.
2.
\(|e|=\frac{d \Phi}{d t}=\frac{0.2 \times 10^{-2}}{0.1}=0.02 \quad V\)
3.
1 weber = 108 Maxwell
4.
\(\Phi=B A \cos \Phi=\left(\frac{F}{I l}\right) A=\frac{M L T^{-2}}{A L} \cdot L^2\)
\(=\left[M L^2 T^{-2} A^{-1}\right]\)
5.
The magnetic flux is maximum when area is held perpendicular to the direction of magnetic field.
6.
(d)
changing a.c. voltages
7.
(d)
transformer
8.
(a)
speed of rotation of coil
9.
(a)
\(\frac { 1 }{ R } \sqrt { \frac { L }{ C } } \)
10.
(b)
> 10ohm
11.
(c)
\(\frac { R }{ L } \)
12.
(a)
1 V
13.
(d)
Transformers
14.
(d)
change in magnetic flux
15.
(a)
which normal to surface area makes with the direction of magnetic field
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