C.O.E. in Induction

Q.

A simple pendulum of mass m and charge q is hanging from the roof of a car moving on a circular track of. Radius r with a speed v . At equillibrium pendulum string makes angle a with equillibrium . Find magnitude and direction of E required so that the string makes same angle a on other side of vertical

Q. In the figure, the switch $S$ is closed so that a current flows in the iron-core inductor which has inductance $L$ and the resistance $R$. When the switch is opened, a spark is obtained in it at the contacts. The spark is due to

1. a slow flux change in $L$
2. a sudden increase in the emf of the battery $B$
3. a rapid flux change in $L$
4. a rapid flux change in $R$

Q. A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in horizontal direction so that the pendulum now swings through the field, the pendulum will

1. Keep oscillating with a smaller time period
2. Keep oscillating with a larger time period
3. Come to rest very soon
4. Keep oscillating with the old time period

Q. 7.A uniform magnetic field B is normal to the surface generated by the track of width l and inclined at an angle theta with horizontal. An inductor of inductance L connects the tops ends as shown in the figure. A frictionless conducting rod of mass m is released at rest. There is no resistance anywhere. The rod is found to executed SHM. Then (A) Amplitude of oscillation is (B) Time period (C)equation of motion (D) current as function of distance x travelled by the rod on track (intial position being x=0 )

Q. 30.a simple pendulum with bob of mass m and conducting wire of length l swings under gravity through an angle 2Q. the earths magnetic field component in the direction perpendicular to swing is b. tctrlhectrl maximum potential difference induced across the pendulum is

Q. A pendulum bob of mass 80 mg , carrying a charge of 2\ast10^{-8} C is at rest in a uniform , horizontal electric field of 20kV/m.Find tension in the thread?

Q. Assertion :In common base configuration the current gain of the transistor is less than unity. Reason: The collector terminal is reverse biased for amplification.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q. A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in horizontal direction so that the pendulum now strings through the field, the pendulum will

1. Keep oscillating with the old time period
2. Keep oscillating with a smaller time period
3. Keep oscillating with a larger time period
4. come to rest very soon

Q. For the circuit shown in fig. four cells are arranged. In Column I, the cell number is given, while in Column II, some statements related to cells are given. Match the entries of Column I with the entries of Column II.

Q. The current flowing through an unloaded voltage divider is called the:

1. resistor current
2. load current
3. bleeder current
4. voltage current

Q. A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in horizontal direction so that the pendulum now swings through the field, the pendulum will

1. Keep oscillating with the old time period
2. Keep oscillating with a smaller time period
3. Keep oscillating with a larger time period
4. Come to rest very soon

Q. What are the advantages of using soft iron as a core, instead of steel, in the coils of galvanometers?

Q.

A conducting ring is placed around the core of an electromagnet as shown in fig. When key K is pressed, the ring

1. Remain stationary
2. Is attracted towards the electromagnet
3. None of the above
4. Jumps out of the core

Q. Initially, the switch is in position 1 for a long time and then shifted to position 2 at $t=0$ as shown in figure. Just after closing switch, the magnitude of current through the capacitor is :

1. zero
2. $\frac{E}{2R}$
3. $\frac{E}{R}$
4. None of these

Q. A simple pendulum of length l is displaced by an angle a and released then work done by simple pendulum in complete vibration

Q. A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected acrose the given cell, has values of
(i) infinity (ii) $9.5\Omega$
The 'balancing lengths, on the potentiometer wire are found to be 3m and 2.85 m, respectively.The value of internal resistance of the cell is

1. $0.25\Omega$
2. $0.95\Omega$
3. $0.75\Omega$
4. $0.5\Omega$

Q. In the figure, the switch $S$ is closed so that a current flows in the iron-core inductor which has inductance $L$ and the resistance $R$. When the switch is opened, a spark is obtained in it at the contacts. The spark is due to

1. a slow flux change in $L$
2. a sudden increase in the emf of the battery $B$
3. a rapid flux change in $L$
4. a rapid flux change in $R$

Q. Given : A and B are input terminals.
Logic $1=>5V$
Logic $0=<1V$
Which logic gate operation, the following circuit does?

1. AND Gate
2. OR Gate
3. XOR Gate
4. NOR Gate

Q. ntA simple pendulum with bob of mass m and conducting wire of Length L swings under gravity through an angle 2theta.The earths magetic field component in the direction perpendicular to swing is B.The maximum potential difference induced across the pendulum isn

Q. When an electric cell drives current through load resistance, its back emf,

1. Supports the original emf
2. Opposes the original emf
3. Supports if internal resistance is low
4. Opposes if load resistance is large

Q. A parallel plate capacitor is connected across a 2 V battery and charged. The battery is then disconnected and a glass slab is introduced between plates. Which of the following pairs of quantities decreases?

1. Charge and potential difference.
2. Potential difference and energy stored.
3. Energy stored and capacitance.
4. Capacitance and charge.

Q. In the circuit shown the capacitor and inductor do not have energy initially. Then

1. the current flowing through the battery at t = 0 is $2\epsilon /3R$
2. the current flowing through the battery at t = 0 is $\epsilon /2R$
3. the current flowing through the battery at t = $\infty$ is $\epsilon /2R$
4. the current flowing through the battery at t = $\infty$ is $2\epsilon /5R$

Q. In the circuit shown, switch is placed in position 1, till the capacitor is charged to half of the maximum possible charge in this situation. Now the switch $S$ is placed in position 2. The maximum energy lost by the circuit after switch S is placed in position 2 is

1. $\frac{1}{2}{CE}^2$
2. $\frac{1}{8}{CE}^2$
3. $\frac{7}{8}{CE}^2$
4. $\frac{9}{8}{CE}^2$

Q. Which of the following is correct statement for voltage gain of n-p-n transistor in common emitter configuration?

1. $A_V$ increases continuously with increase in input voltage.
2. $A_V$ is high, then decreases, then increases and becomes constant with increase in input voltage.
3. $A_V$ remains constant with increase in input voltage.
4. $A_V$ remains almost zero, then increases, decreases and again becomes zero with increase in input voltage.