When a coil is rotated in a uniform magnetic field at a
certain frequency, the variation with time t of the induced
emf, E, is shown below.When a coil is rotated in a uniform magnetic field at a
certain frequency, the variation with time t of the induced
emf, E, is shown below.
The frequency of rotation of the coil is reduced to one half of its initial value. Which one of the graphs at right best shows the new variation with time t of the induced emf, E.
The magnetic flux F
through a coil of 500 turns varies with time as shown below.
The voltage induced in the coil is....
a ... 0.25 V
b ... 0.50 V
c ... 250 V
d ... 1000 V
A simple
electric generator is shown at right. A single coil is rotated
as indicated between magnetic poles N and S. Electrical contact
with an external circuit is maintained through brushes touching
slip rings B.
At the instant when the rotating coil is oriented as shown, the output emf of the generator....
a .... reverses direction.
b .... has the same value as in any other orientation of the coil.
c .... is zero.
d .... has its maximum value.
Two coils
of different diameters are in the same uniform magnetic field
B.
If the magnitude of the magnetic field is increasing with time....
a ...the induced emf would be the same in each coil.
b ... the induced emf in coil 1 would be greater.
c ... the induced emf in coil 2 would be greater.
d ... the induced emf in the two coils would be in opposite directions.
A simple AC alternator is made by rotating a flat rectangular
coil in a uniform magnetic field as shown.
The maximum emf produced is V.
If the frequency of rotation is doubled the maximum emf produced is....
a ... V.
b ... 1.42V.
c ... 2V.
d ... 4V.
A metal
rod is moving at a steady speed perpendicular to a magnetic
field as shown.
In the steady state situation, when the rod moves steadily, the electron experiences (apart from gravity)....
a ... both an electric and a magnetic force.
b ... neither an electric nor a magnetic force.
c ... a magnetic force only.
d ... an electric force only.
An AC generator produces a sinusoidal output e.m.f. If the
frequency of rotation of the generator coil is doubled then the
peak voltage....
a ... remains unchanged.
b ... halves.
c ... increases by a factor of root 2.
d ... doubles.
A
long straight wire is in the plane of a rectangular loop of
wire. The straight wire carries a constant current I (as shown
in the figure) and is moved towards the rectangular loop.
While the wire is being moved towards the rectangular loop the, the current in the loop...
a ... is always zero
b ... flows clockwise round the loop.
c ... flows counterclockwise round the loop.
d ... alternates, first one way then the opposite way around the loop.
A
loop made of conducting material is rotated about the vertical
axis XY. At all times during the rotation the loop is in a region
of uniform magnetic field.
At a particular instant, (in the position shown), the plane of the loop is parallel to the uniform magnetic field.
At this instant which one of the following about the induced current is true?
a ... The induced current in the loop is a maximum and the flux linking the loop is a maximum.
b ... The induced current in the loop is a maximum and the flux linking the loop is zero.
c ... The induced current in the loop is zero and the flux linking the loop is zero.
d ...The induced current in the loop is zero and the flux linking the loop is a maximum.
In the arrangement
show at right, if the current in the straight wire is increasing
with time, the current induced in the loop will be....
a ... zero.
b ... clockwise.
c ... anti-clockwise.
d ... alternating.
The
diagram shows a simple generator with the coil rotating between
magnetic poles. Electrical contact is maintained through two brushes
each touching a slip ring.
At the instant when the rotating coil is positioned as shown, the voltage across the brushes...
a ... is zero.
b ... has its maximum value.
c ... has the same constant value as in all other orientations.
d ... reverses direction.
Two
coils, X and Y, in the circuits shown are placed next to each
other. G is a center zero galvanometer and S is a switch.
What will happen to the galvanometer needle if the switch S is closed, kept closed for a while, and then opened again?
a It will deflect to one side, remain steady, and then move back to zero.
b It will not move.
c It will deflect to one side and remain there.
d It will deflect to one side, back to zero, then to the other side, and back to zero.
A metal rod of length l is moved at constant speed
v at right angles to a uniform magnetic field of strength
B.
The work done in moving an electron of charge e from one end of the rod to the other is....
a ... zero.
b ... Blve.
c ... Blv.
d ... Bev.
A
rectangular loop of wire is moved from left to right through
a uniform magnetic field directed into the paper as shown in the
diagram at right.
Which one of the following correctly gives the direction of the current in the loop as the side QR enters the field and as the side QR leaves the field?
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