Physics-
General
Easy
Question
PQ is an infinite current carrying conductor. AB and CD are smooth conducting rods on which a conductor EF moves with constant velocity V as shown. The force needed to maintain constant speed of EF is.
The correct answer is:
Related Questions to study
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A wooden stick of length 
is rotated about an end with constant angular velocity 
in a uniform magnetic field B perpendicular to the plane of motion. If the upper one third of its length is coated with copper, the potential difference across the whole length of the stick is
A wooden stick of length is rotated about an end with constant angular velocity in a uniform magnetic field B perpendicular to the plane of motion. If the upper one third of its length is coated with copper, the potential difference across the whole length of the stick is
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In the figure shown a square loop PQRS of side 'a' and resistance 'r' is placed near an infinitely long wire carrying a constant current I. The sides PQ and RS are parallel to the wire. The wire and the loop are in the same plane. The loop is rotated by 
about an axis parallel to the long wire and passing through the mid points of the side QR and PS. The total amount of charge which passes through any point of the loop during rotation is :
In the figure shown a square loop PQRS of side 'a' and resistance 'r' is placed near an infinitely long wire carrying a constant current I. The sides PQ and RS are parallel to the wire. The wire and the loop are in the same plane. The loop is rotated by about an axis parallel to the long wire and passing through the mid points of the side QR and PS. The total amount of charge which passes through any point of the loop during rotation is :
physics-General
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Two metallic rings A and B, identical in shape and size but having different resistivities 
and 
, are kept on top of two identical solenoids as shown in the figure. When current I is switched on in both the solenoids in identical manner, the rings A and B jump to heights hA and hB , respectively, with 
. The possible relation(s) between their resistivities and their masses 
and 
is(are)
Two metallic rings A and B, identical in shape and size but having different resistivities and , are kept on top of two identical solenoids as shown in the figure. When current I is switched on in both the solenoids in identical manner, the rings A and B jump to heights hA and hB , respectively, with . The possible relation(s) between their resistivities and their masses and is(are)
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The figure shows certain wire segments joined together to form a coplanar loop. The loop is placed in a perpendicular magnetic field in the direction going into the plane of the figure. The magnitude of the field increases with time. 
and 
are the currents in the segments ab and cd. Then,
The figure shows certain wire segments joined together to form a coplanar loop. The loop is placed in a perpendicular magnetic field in the direction going into the plane of the figure. The magnitude of the field increases with time. and are the currents in the segments ab and cd. Then,
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Statement -1 A vertical iron rod has a coil of wire wound over it at the bottom end. An alternating current flows in the coil. The rod goes through a conducting ring as shown in the figure. The ring can float at a certain height above the coil.
Statement - 2 In the above situation, a current is induced in the ring which interacts with the horizontal component of the magnetic field to produce an average force in the upward direction
Statement -1 A vertical iron rod has a coil of wire wound over it at the bottom end. An alternating current flows in the coil. The rod goes through a conducting ring as shown in the figure. The ring can float at a certain height above the coil.
Statement - 2 In the above situation, a current is induced in the ring which interacts with the horizontal component of the magnetic field to produce an average force in the upward direction
physics-General
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Electrical resistance of certain materials, known as superconductors, changes abruptly from a nonzero value to zero as their temperature is lowered below a critical temperature 
(0). An interesting property of superconductors is that their critical temperature becomes smaller than (0) if they are placed in a magnetic field, i.e., the critical temperature (B) is a function of the magnetic field strength B. The dependence of (B) on B is shown in the figure
A superconductor has (0) = 100 K. When a magnetic field of 7.5 Tesla is applied, its decreases to 75 K. For this material one can definitely say that when :
Electrical resistance of certain materials, known as superconductors, changes abruptly from a nonzero value to zero as their temperature is lowered below a critical temperature (0). An interesting property of superconductors is that their critical temperature becomes smaller than (0) if they are placed in a magnetic field, i.e., the critical temperature (B) is a function of the magnetic field strength B. The dependence of (B) on B is shown in the figure
A superconductor has (0) = 100 K. When a magnetic field of 7.5 Tesla is applied, its decreases to 75 K. For this material one can definitely say that when :
physics-General
physics-
Electrical resistance of certain materials, known as superconductors, changes abruptly from a nonzero value to zero as their temperature is lowered below a critical temperature (0). An interesting property of superconductors is that their critical temperature becomes smaller than (0) if they are placed in a magnetic field, i.e., the critical temperature (B) is a function of the magnetic field strength B. The dependence of (B) on B is shown in the figure
In the graphs below, the resistance R of a superconductor is shown as a function of its temperature T for two different magnetic fields 
(solid line) and 
(dashed line). If is larger than , which of the following graphs shows the correct variation of R with T in these fields?
Electrical resistance of certain materials, known as superconductors, changes abruptly from a nonzero value to zero as their temperature is lowered below a critical temperature (0). An interesting property of superconductors is that their critical temperature becomes smaller than (0) if they are placed in a magnetic field, i.e., the critical temperature (B) is a function of the magnetic field strength B. The dependence of (B) on B is shown in the figure
In the graphs below, the resistance R of a superconductor is shown as a function of its temperature T for two different magnetic fields (solid line) and (dashed line). If is larger than , which of the following graphs shows the correct variation of R with T in these fields?
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The capacitor of capacitance C can be charged (with the help of a resistance R) by a voltage source V, by closing switch 
while keeping switch 
open. The capacitor can be connected in series with an inductor ‘L’ by closing switch and opening .
After the capacitor gets fully charged, is opened and is closed so that the inductor is connected in series with the capacitor. Then,
The capacitor of capacitance C can be charged (with the help of a resistance R) by a voltage source V, by closing switch while keeping switch open. The capacitor can be connected in series with an inductor ‘L’ by closing switch and opening .
After the capacitor gets fully charged, is opened and is closed so that the inductor is connected in series with the capacitor. Then,
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The capacitor of capacitance C can be charged (with the help of a resistance R) by a voltage source V, by closing switch while keeping switch open. The capacitor can be connected in series with an inductor ‘L’ by closing switch and opening .
Initially, the capacitor was uncharged. Now, switch is closed and is kept open. If time constant of this circuit is 
, then
The capacitor of capacitance C can be charged (with the help of a resistance R) by a voltage source V, by closing switch while keeping switch open. The capacitor can be connected in series with an inductor ‘L’ by closing switch and opening .
Initially, the capacitor was uncharged. Now, switch is closed and is kept open. If time constant of this circuit is , then
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An inductor (L = 0.03H) and a resistor (R = 0.15 k
) are connected in series to a battery of 15V EMF in a circuit shown below. The key 
has been kept closed for a long time. Then at t = 0, is opened and key 
is closed simultaneously. At t = 1 ms, the current in the circuit will be (
=150)
An inductor (L = 0.03H) and a resistor (R = 0.15 k) are connected in series to a battery of 15V EMF in a circuit shown below. The key has been kept closed for a long time. Then at t = 0, is opened and key is closed simultaneously. At t = 1 ms, the current in the circuit will be ( =150)
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In the circuit shown here, the point ‘C’ is kept connected to point ‘A’ till the current flowing through the circuit becomes constant. Afterward, suddenly, point ‘C’ is disconnected from point ‘A’ and connected to point ‘B’ at time t = 0. Ratio of the voltage across resistance and the inductor at t = L/R will be equal to :
In the circuit shown here, the point ‘C’ is kept connected to point ‘A’ till the current flowing through the circuit becomes constant. Afterward, suddenly, point ‘C’ is disconnected from point ‘A’ and connected to point ‘B’ at time t = 0. Ratio of the voltage across resistance and the inductor at t = L/R will be equal to :
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In an LCR circuit as shown below both switches are open initially. Now switch is closed, kept open. (q is charge on the capacitor and 
is Capacitive time constant). Which of the following statement is correct?
In an LCR circuit as shown below both switches are open initially. Now switch is closed, kept open. (q is charge on the capacitor and is Capacitive time constant). Which of the following statement is correct?
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A metallic rod of length ‘l’ is tied to a string of length 2l and made to rotate with angular speed on a horizontal table with one end of the string fixed. If there is a vertical magnetic field ‘B’ in the region, the e.m.f. induced across the ends of the rod is:
A metallic rod of length ‘l’ is tied to a string of length 2l and made to rotate with angular speed on a horizontal table with one end of the string fixed. If there is a vertical magnetic field ‘B’ in the region, the e.m.f. induced across the ends of the rod is:
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physics-
A rectangular loop has a sliding connector PQ of length 
and resistance R and it is moving with a speed v as shown. The set-up is placed in a uniform magnetic field going into the plane of the paper. The three currents 
and I are :
A rectangular loop has a sliding connector PQ of length and resistance R and it is moving with a speed v as shown. The set-up is placed in a uniform magnetic field going into the plane of the paper. The three currents and I are :
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An inductor of inductance L = 400 mH and resistors of resistances R1 = 2 and R2 = 2 are connected to a battery of emf 12 V as shown in the figure. The internal resistance of the battery is negligible. The switch S is closed at t = 0. The potential drop across L as a function of time is 
An inductor of inductance L = 400 mH and resistors of resistances R1 = 2 and R2 = 2 are connected to a battery of emf 12 V as shown in the figure. The internal resistance of the battery is negligible. The switch S is closed at t = 0. The potential drop across L as a function of time is
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