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Questions asked by priyanka.c
Questions
2867
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Consider a magnet surrounded by a wire with an on/off switch as shown in the fig. If the switch is thrown from the off position (open circuit) to the on position (closed circuit) will a current flow in the circuit ? Explain.
(a) Yes
(b) No
(c) Cannot be determine
(d) information not sufficient
cbsc
class12
physics
electromagnetic-induction
sec-b
exemplar
medium
asked
Dec 31, 2016
1
answer
A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. The can be cause
(a) The magnetic field is constant
(b) The magnetic field is in the same plane as the circular coil and it may or may not vary
(c) The magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is decreasing suitably.
(d) There is constant magnetic field in the perpendicular (to the plane of the coil) direction
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
easy
asked
Dec 31, 2016
1
answer
The mutual inductance $M_{12}$ of coil 1 with respect to coil 2.
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
easy
asked
Dec 31, 2016
1
answer
An emf is produced in a coil, which is not connected to an external voltage source. This can be due to <br/(a) the coil being in a time varying magnetic field
(b) the coil moving in a time varying magnetic field
(c) the coil moving in a constant magnetic field
(d) the coil is stationary in external spatially varying magnetic field, which does not change with time.
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
easy
asked
Dec 31, 2016
1
answer
An $emf$ is produced in a coil, which is not connected to an external voltage source. This can be due to
(a) The coil being in a time varying magnetic field
(b) The coil moving in a time varying magnetic field
(c) The coil moving in a constant magnetic field
(d) The coil is stationary is externally spatially varying magnetic field, which does not change with time.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
exemplar
easy
asked
Dec 31, 2016
1
answer
A metal plate is getting heated. It can be because of
(a) a direct current is passing through the plate.
(b) it is placed in a times varying magnetic field
(c) it is placed in a space varying magnetic field but does not varying with time
(d) a current (either direct or alternating ) is passing through the plate.
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
easy
asked
Dec 31, 2016
1
answer
The self inductance L of a solenoid of length $l$ and area of cross section A, with a fixed number of turns N increases as
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
easy
asked
Dec 31, 2016
1
answer
There are two coils A and B. A current starts flowing in B, the coil A is made to rotate about a vertical axis as shown in the fig. No current flows in B if A is at rest. The current in the coil A, when the current in B (at t = 0) is counter clockwise and the coil A is as shown at this instant t= 0 is
(a) constant current clockwise
(b) varying current clockwise
(c) varying current clockwise<br> (d) constant current counter clockwise.
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
medium
asked
Dec 31, 2016
1
answer
There are two coils A and B as shown in fig. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counter-clockwise. B is kept stationary when A moves. We can infer that
(a) there is a constant current in the anticlockwise direction in A (b) there is a varying current in A
(c) there is no current in A
(d) there is a constant current in the counter clockwise direction in A
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
medium
asked
Dec 31, 2016
1
answer
A cylindrical bar magnet is rotated about its axis, as shown in fig. A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then
(a) a direct current flows in the ammeter A
(b) an alternating sinusoidal current flows through the ammeter A with a time period $T= \frac{2T}{w}$
(c) no current flows through the ammeter A
(d) a time varying non-sinusoidal current flows through the ammeter A
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
medium
asked
Dec 31, 2016
1
answer
A loop, made of straight edges has six corner at A(0, 0, 0), B(L, 0, 0), C(L, L, O), D(O, L,O), E(O, L, L) and F (0, 0, L). A magnetic field $B = B_o(\hat{i} + \hat{k})T$ is present in the region.
The flux passing through the loop ABCDEFA (in that order) is $(a)B_oL^2Wb$ $(b)2B_oL^2Wb$ $(c)\sqrt 2B_oL^2Wb$ $(d)4B_oL^2Wb$
cbsc
class12
physics
electromagnetic-induction
sec-b
exemplar
medium
asked
Dec 31, 2016
1
answer
A square of side L metres lies in the x-y plane in a region, where the magnetic field is given by $B = B_o (2 \hat{i} +3 \hat{j} + 4 \hat{k}) T,$ where $B_o$ is constant. The magnitude of flux passing through the square $(a)\; 2B_oL^2 Wb$ $(b) \; 3B_o L^2 Wb$ $(c) \; 4B_o L^2 Wb$ $(d) \; \sqrt{29}B_o L^2 Wb$
cbsc
class12
physics
electromagnetic-induction
sec-a
exemplar
easy
asked
Dec 31, 2016
1
answer
Evaluate the induced $emf$ in the loop if the wire carries a current of 50A and the loop has an instantaneous velocity $v = 10 m/s$ at the location $x= 0.2 m,$ as shown, Take $a = 0.1$ and assume that the loop has a large resistance.
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 31, 2016
1
answer
Obtain an expression for the mutual inductance between a long straight wire and a square of side a as shown in the figure .
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
difficult
asked
Dec 31, 2016
1
answer
An air-cored solenoid with length 30cm, area of cross section $25 cm^2$ and number of turns 500, carries a current of 2.5A. The current is suddenly switched off in a brief time of $10^{-3}S.$ How much is the average back emf induced across the ends of the open switch in the circuit ? Ignore the variation in magnetic field near the ends of the solenoid ?
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
difficult
asked
Dec 31, 2016
1
answer
How much power is dissipated as heat in the closed circuit ? What is the source of this power ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
medium
asked
Dec 31, 2016
1
answer
Figure shows a metal rod PQ resting on the smooth rail AB and positioned between the poles of a permanent magnet. The rail, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = $9.0 m \Omega$. Assume the field to be uniform.
What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
medium
asked
Dec 31, 2016
1
answer
Figure shows a metal rod PQ resting on the smooth rail AB and positioned between the poles of a permanent magnet. The rail, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = $9.0 m \Omega$. Assume the field to be uniform.
How much power is required at the same speed, to keep the rod moving at the same speed. (=12 cm/s) when k is closed ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 31, 2016
1
answer
Figure shows a metal rod PQ resting on the smooth rail AB and positioned between the poles of a permanent magnet. The rail, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = $9.0 m \Omega$. Assume the field to be uniform.
what is the retarding force on the rod when k is closed ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 31, 2016
1
answer
Figure shows a metal rod PQ resting on the smooth rail AB and positioned between the poles of a permanent magnet. The rail, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = $9.0 m \Omega$. Assume the field to be uniform.
With k open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 31, 2016
1
answer
Figure shows a metal rod PQ resting on the smooth rail AB and positioned between the poles of a permanent magnet. The rail, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = $9.0 m \Omega$. Assume the field to be uniform.
Is there an excess charge built up at the ends of rods, when k is open ? What if k is closed ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 31, 2016
1
answer
Figure shows a metal rod PQ resting on the smooth rail AB and positioned between the poles of a permanent magnet. The rail, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = $9.0 m \Omega$. Assume the field to be uniform.
Suppose K is open and the rod is moved with a speed of 12cm/s in the direction shown. Give the polarity and magnitude of the induced $emf$.
cbsc
class-12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 31, 2016
1
answer
It is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet. A small flat search coil of area $2cm^2$ with closely wound turns, is positioned normal to the field direction and then quickly snatched out of the field region. Equivalently one can give it a quick $90^{\circ}$ turns to bring its plane parallel to the field direction. The total change flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5mc. The combined resistance of the coil and the galvanometer $0.50 \Omega$. Estimate the field strength of magnet.
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
medium
asked
Dec 30, 2016
1
answer
A square loop of side 12cm with its sides parallel to X and Y axes is moved with a velocity of 8 cm/s in the positive X-direction in an environment containing a magnetic field in the positive Z-direction. The field is neither uniform in space nor constant in time. It has a gradient of $10^{-3}$T/cm along the negative X-direction (that is it increases by $10^{-3}$T/cm as one moves in the negative X-direction) and it is decreasing in time at the rate of $10^{-3} $ T/S. Determine the direction and magnitude of the induced current in the loop if its resistance is $4.50 m\Omega$
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
difficult
asked
Dec 30, 2016
1
answer
Suppose a rectangular loop of sides 8cm and 2cm with a small cut is stationary but the current feeding the electromagnet that produces the magnetic field is gradually reduced so that the field decreases from its initial value of 0.3T at the rate of 0.02T/S. If the cut is joined and the loop has a resistance of 1.6$ \Omega$, how much power is dissipated by the loop as heat? What is the source of this power ?
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
difficult
asked
Dec 30, 2016
1
answer
A jet plane is travelling towards west at a speed of $1800\; km/hr$. What is the voltage difference developed between the ends of the wing having a span of 25m, if the earth's magnetic field at the location has a magnitude of $5 \times 10^{-4} T$ and the dip angle is $30^{\circ}$
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
difficult
asked
Dec 30, 2016
1
answer
A pair of adjacent coils have a mutual inductance of 1.5 H. If the current in one is changed from $0 \; to\; 20 A$ is $0.5 S$ , what is the change of flux with the other coil.
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 30, 2016
1
answer
A horizontal straight wire $10 \;cm$ long expending from east to west is falling with a speed of $5.0\; m/s $ at right angles to the horizontal component of the earth's magnetic field $0.30 \times 10^{-4}\;wb/m^2$. Which end of the wire is at the higher electrical potential ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 30, 2016
1
answer
A horizontal straight wire $10 \;cm$ long expending from east to west is falling with a speed of $5.0\; m/s $ at right angles to the horizontal component of the earth's magnetic field $0.30 \times 10^{-4}\;wb/m^2$. What is the direction of the induced $emf$.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 30, 2016
1
answer
Current in a circuit falls from $5.0 A$ to $0.0 A$ in $0.1 S$. If an average $emf$ of $ 200 V$ induced, given an estimate of the self-inductance of the circuit.
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 30, 2016
1
answer
A horizontal straight wire $10 \;cm$ long expending from east to west is falling with a speed of $5.0\; m/s $ at right angles to the horizontal component of the earth's magnetic field $0.30 \times 10^{-4}\;wb/m^2$. What is the instantaneous value of the $emf$ induced in the wire ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 30, 2016
1
answer
A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, where does the power come from ?
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
medium
asked
Dec 30, 2016
1
answer
A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, calculate the average power loss due to Joule heating.
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
medium
asked
Dec 30, 2016
1
answer
A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, calculate the maximum value of current in the coil.
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
difficult
asked
Dec 29, 2016
1
answer
A $1.0m $ long metallic rod is rotated with an angular frequency of $400 rad/s$ about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of $0.5 \;T$ parallel to the axis exists everywhere. Calculate the $emf$ developed between the centre and the ring.
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 29, 2016
1
answer
A rectangular wire loop of slides $8 \;cm$ and $2\;cm$ with a small cut is moving out of a region of uniform field of magnitude $0.3T$ directed normal to the loop. What is the $emf$ developed across the cut if the velocity of the loop is $1\;cm/s$ in a direction normal to the shorter side of the loop. For how long does induced voltage last in each case.
cbsc
class-12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 29, 2016
1
answer
A rectangular wire loop of slides $8 \;cm$ and $2\;cm$ with a small cut is moving out of a region of uniform field of magnitude $0.3T$ directed normal to the loop. What is the $emf$ developed across the cut if the velocity of the loop is $1\;cm/s$ in a direction normal to the longer side. How long will the induced current $V$ last.
cbsc
class12
physics
electromagnetic-induction
sec-b\ncert\medium
asked
Dec 29, 2016
1
answer
A long solenoid with $15\; turns\; per\; cm $ has a small loop of area $2.0cm^2$ placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from $2.0 A \; to \;4.0 A $ in $0.1 S ,$ what is the induced $emf$ in the loop while the current is changing?
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 29, 2016
1
answer
Use Lenz's law to determine the direction of induced current in the situation described by figure.
A circular loop being deformed in a narrow straight wire.
cbsc
class 12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
1
answer
Use Lenz's law to determine the direction of induced current in the situations described by figure
A wire of irregular shape turning into a circular shape.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
1
answer
Current (I) decreasing at a steady state.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
1
answer
Predict the direction of induced current in situation described above.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
1
answer
Rheostat setting being changed.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
1
answer
Predict the direction of induced current in the situation described above.
cbsc
class 12
physics
electromagnetic-induction
sec-a ncert easy
asked
Dec 29, 2016
1
answer
Predict the direction of induced current in the situation described above.
cbsc
class-12
physcis
electromagnetic-induction
sec-a ncert easy
asked
Dec 29, 2016
1
answer
Predict the direction of induced current in the situation described above
cbsc
class12
physics
electromagnetic induction
sec-a
ncert
easy
asked
Dec 29, 2016
1
answer
If the points $(1,1,p)$ and $(-3,0,1)$ are at equidistant from the plane $\overrightarrow {r} . (3 \hat {i} +4 \hat {j} -12 \hat {k}) + 13 = 0, $ then find the value of p.
cbse
class12
maths
ch10
sec-c
asked
Dec 28, 2016
1
answer
Form the differential equation of the family of circles in the first quadrant which touch the coordinate axes.
cbse
class12
maths
ch9
sec-c
asked
Dec 27, 2016
1
answer
An oil company has two depots A and B with capacities of 7000 L and 4000 L respectively. The company is to supply oil to three petrol pumps, D, E and F whose requirements are 4500L, 3000L and 3500L respectively. Assuming that the transportation cost of 10 litres of oil is Rs 1 per km, How should the delivery be scheduled in order that the transportation cost is minimum ? What is the minimum cost? The distance (In km) between the depots and the petrol pumps is given in the following table :
cbse
class12
maths
ch1
sec-e
asked
Dec 27, 2016
1
answer
Suppose a girl throws a die. If she throws a 5 or 6, she tosses a coin 3 times and notes the number of heads. If she gets 1, 2, 3 or 4, she tosses a coin once and notes whether a head or tail is obtained. If she obtained exactly one head, what is the probability that she threw 1, 2, 3 or 4 with a die?
cbse
class12
maths
ch13
sec-e
asked
Dec 27, 2016
1
answer
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