Recent questions in Physics

Write the truth table for the circuit given

asked Jan 1, 2017 by meena.p

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Write the logic operation for the below circuit :

asked Jan 1, 2017 by meena.p

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write the truth table for the circuit below :

asked Jan 1, 2017 by meena.p

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Identify the exact logic operation carried out by the circuit below

asked Jan 1, 2017 by meena.p

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write the truth table for a NAND gate for the fig given

asked Jan 1, 2017 by meena.p

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ODBAC is a fixed rectangular conductor of negligible resistance (co is not connected) and OP is a conductor which rotates clockwise with an angular velocity $w$ as shown in the fig. The entire system is in a uniform magnetic field B whose direction is along the normal to the surface of the rectangular conductor ABDC. The conductor OP is in electric contact with ABDC. The rotating conductor has resistance of X per unit length. Find the current in the rotating conductor as it rotates by $180^{\circ}$

asked Jan 1, 2017 by priyanka.c

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A conducting wire XY of mass $m$ and negligible resistance slides smoothly on two parallel conducting wire as shown in the fig. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field $B = B (+) \hat {k}$ . Is there a decrease in kinetic energy of XY equalling the heat lost in R ?

asked Jan 1, 2017 by priyanka.c

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A conducting wire XY of mass $m$ and negligible resistance slides smoothly on two parallel conducting wire as shown in the fig. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field $B = B (+) \hat {k}$ If B is independent of time, obtain $V (t)$ assuming $V(0) = u_0$

asked Jan 1, 2017 by priyanka.c

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A magnetic field $B =B_o \sin(wt) \hat{k}$ covers a large region where a wire AB slides smoothly over two parallel conductors separated by a distance d, as shown in the fig. The wire are in the x-y plane. The wire AB (of length d) has resistance R and the parallel wires have negligible resistance. It AB is moving velocity $v$ , what is the force needed to keep the wire at constant velocity ?

asked Jan 1, 2017 by priyanka.c

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A conducting wire XY of mass $m$ and negligible resistance slides smoothly on two parallel conducting wire as shown in the fig. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field $B = B (+) \hat {k}$ write down the equation for the acceleration of the wire XY.

asked Jan 1, 2017 by priyanka.c

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Consider a metal ring kept (supported by a cardboard) on top of a fixed solenoid carrying a current $I$ as shown in the fig : The centre of the ring coincides with the axis of the solenoid. If the current in the solenoid is switched off, What happens to the ring ?

asked Jan 1, 2017 by priyanka.c

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Consider a metal ring kept on top of a fixed solenoid (say on a cardboard) as shown in the figure. The centre of the ring coincides with the axis of the solenoid. If the current is suddenly switched on, the metal ring jumps up. Explain.

asked Dec 31, 2016 by priyanka.c

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A solenoid is connect to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, will the current increases or decreases ? Explain ?

asked Dec 31, 2016 by priyanka.c

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A wire in the form of a tightly wound solenoid is connected to DC source, and carries a current. If the coil is stretched so that spiral coil, will the current increases or decreases ? Explain.
(a) the current drawn from the d.c source increases
(b) the current drawn from d.c source decreases
(c) the current drawn first increases and then decreases
(d) the current drawn first decreases and then increases

asked Dec 31, 2016 by priyanka.c

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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

asked Dec 31, 2016 by priyanka.c

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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

asked Dec 31, 2016 by priyanka.c

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The mutual inductance $M_{12}$ of coil 1 with respect to coil 2.

asked Dec 31, 2016 by priyanka.c

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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.

asked Dec 31, 2016 by priyanka.c

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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.

asked Dec 31, 2016 by priyanka.c

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.

asked Dec 31, 2016 by priyanka.c

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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

asked Dec 31, 2016 by priyanka.c

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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.

asked Dec 31, 2016 by priyanka.c

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Equipotentials at a great distance from a collection whose total sum is not zero are approximately

asked Dec 31, 2016 by meena.p

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The electrostatic potential on the surface of a charged conducting sphere is $100\;V$ . Two statements are made in this regard: S1: At any point inside the sphere , electric intensity is zero . S2: At any point inside the sphere ,the electro potential is 100 V. Which of the following is a correct statement ?

asked Dec 31, 2016 by meena.p

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Figure shows some equipotential lines distributed in space .A charged object is moved from point A and point B.

asked Dec 31, 2016 by meena.p

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A positively charged particle is released from rest in an unifrom electric field . The electric potential energy of the charge

asked Dec 31, 2016 by meena.p

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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

asked Dec 31, 2016 by priyanka.c

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A capacitor of $4 \;\mu F$ is connected as shown in the figure . The internal resistance of the battery is $5.0 \Omega$ . The amount of charge on the capacitor plates will be

asked Dec 31, 2016 by meena.p

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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

asked Dec 31, 2016 by priyanka.c

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In a npn transistor circuit, the collector current is $10\;mA$ . If $95\%$ of the electrons emitted reach the collector, Which of the following statements are true ?

asked Dec 31, 2016 by meena.p

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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 $(a)B_oL^2Wb$ $(b)2B_oL^2Wb$ $(c)\sqrt 2B_oL^2Wb$ $(d)4B_oL^2Wb$

asked Dec 31, 2016 by priyanka.c

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What happens during regulation action of a Zenerdiode ?

asked Dec 31, 2016 by meena.p

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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 $(a)\; 2B_oL^2 Wb$ $(b) \; 3B_o L^2 Wb$ $(c) \; 4B_o L^2 Wb$ $(d) \; \sqrt{29}B_o L^2 Wb$

asked Dec 31, 2016 by priyanka.c

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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.

asked Dec 31, 2016 by priyanka.c

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Obtain an expression for the mutual inductance between a long straight wire and a square of side a as shown in the figure .

asked Dec 31, 2016 by priyanka.c

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A $220\;V$ A.C supply in connected between points A and B as shown in the figure . What will be the potential difference V across the capacitor ?

asked Dec 31, 2016 by meena.p

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The conductivity of a semiconductor increases with increases in temperature because:

asked Dec 31, 2016 by meena.p

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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 ?

asked Dec 31, 2016 by priyanka.c

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Write the logic operation for the circuit below :

asked Dec 31, 2016 by meena.p

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Identify the logic operation :

asked Dec 31, 2016 by meena.p

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How much power is dissipated as heat in the closed circuit ? What is the source of this power ?

asked Dec 31, 2016 by priyanka.c

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You are given a circuit . Name the output gate

asked Dec 31, 2016 by meena.p

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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?

asked Dec 31, 2016 by priyanka.c

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You are given a circuit . Name the output gate

asked Dec 31, 2016 by meena.p

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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 ?

asked Dec 31, 2016 by priyanka.c

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In p-n junction diode , the current I , can be expressed $I= I_0 exp \bigg[ \large\frac{eV}{K_{B}T}-1 \bigg]$ Where $I_0$ is called the satiation current , V is the voltage across the dicode and in positive for forward bias and negative for reverse bias and I is the current through the dicode , $K_B$ is the BoHZmann constant $(8.6 \times 10^{-5}e^v/k)$ and T is the absolute temperature . If for a given diode $I_0 = 5 \times 10^{-12}A$ and $T=300\;K$ , then what will be the increase in the current if the voltage across the diode is increased to $0.7\;A$ ?what will be the Dynamic resistance

asked Dec 31, 2016 by meena.p

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 ?

asked Dec 31, 2016 by priyanka.c

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In the circuit given below , when the input voltage of the base resistance is $10\;V,V_{BE}$ is zero. and $V_{CE}$ is also zero. Find the value of $I_c$ and $\beta$

asked Dec 31, 2016 by meena.p

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.

asked Dec 31, 2016 by priyanka.c

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 ?

asked Dec 31, 2016 by priyanka.c

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