Faraday's Law

Q. How does a solenoid behave like a magnet? Can you determine the north and south poles of a current carrying solenoid with the help of a bar magnet?

Q. What is the relation between the number of turns in the coil and the emf across their ends?

1. $\frac{E_p}{E_s}=\frac{n_p}{n_s}$
2. $\frac{E_p}{E_s}=\frac{n_s}{n_p}$
3. $E_p+E_s=n_p+n_s$
4. $E_p-E_s=n_p-n_s$

Q.

A wire carrying current $I$ is bent in the shape$ABCDEFA$ as shown, where rectangle $ABCDA$ and $ADEFA$ are perpendicular to each other. If the sides of the rectangles are of lengths $a$ and $b$, then the magnitude and direction of magnetic moment of the loop $ABCDEFA$ is:

1. $\sqrt{2}abI,$along $\left[\frac{{\displaystyle \stackrel{\wedge }{j}}}{\sqrt{5}}+\frac{{\displaystyle 2\stackrel{\wedge }{k}}}{\sqrt{5}}\right]$

2. $abI,$along $\left[\frac{{\displaystyle \stackrel{\wedge }{j}}}{\sqrt{5}}+\frac{{\displaystyle 2\stackrel{\wedge }{k}}}{\sqrt{5}}\right]$

3. $\sqrt{2}abI,$along $\left[\frac{{\displaystyle \stackrel{\wedge }{j}}}{\sqrt{2}}+\frac{{\displaystyle \stackrel{\wedge }{k}}}{\sqrt{2}}\right]$

4. $abI,$along $\left[\frac{{\displaystyle \stackrel{\wedge }{j}}}{\sqrt{2}}+\frac{{\displaystyle \stackrel{\wedge }{k}}}{\sqrt{2}}\right]$

Q. If F is the magnitude of force experienced by a unit charge placed at a distance of 1 cm from an infinitely large charged sheet , then what will be the force experienced by the same charge placed at a distance of 2 cm from the same sheet?

Q.

A planar loop of wire rotates in a uniform magnetic field. Initially at $t=0$, the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of $10s$ about an axis in its plane, then the magnitude of induced emf will be maximum and minimum, respectively at

1. $2.5secand5sec$

2. $5secand7.5sec$

3. $2.5secand7.5sec$

4. $5secand10sec$

Q. Two point charges 5mC and 3mC are at position ( 1 3 2) and (3 5 1) resp find the forces F12 and F21 using vector form of couloumbs law.

Q.

A boat is moving due East in a region where the earths magnetic field is $5.0\times {10}^{-5}N{A}^{-1}{m}^{-1}$ due North and horizontal. The boat carries a vertical aerial $2m$ long. If the speed of the boat is $1.50m{s}^{-1}$, the magnitude of the induced emf in the wire of aerial is

1. $0.75mV$

2. $0.50mV$

3. $0.15mV$

4. $1mV$

Q.

What does inductance depend on?

Q.

In circular coil. when no.of turns is doubled & resistance becomes half of the initial then inductance becomes.

1. $4times$

2. $2times$

3. $8times$

4. No change

Q. A coil having an area $A_0$ is placed in a magnetic field. The field intensity changes from $B_0$ to $4B_0$ in time interval of ‘t’. The magnitude of emf induced in the coil will be _____.

1. $\frac{A_0{B}_0}{t}$
2. $\frac{3A_0{B}_0}{t}$
3. $\frac{3B_0}{A_{0}t}$
4. $\frac{4B_0}{A_{0}t}$

Q.

How can a small current in a circuit be detected?

Q.

A coil has resistance 30 ohm and inductive reactance 20 ohm at 50Hz frequency. If an ac source, of 200volt, 100Hz, is connected across the coil, the current in the coil will be

Q. In alternating current the direction of charge flow reverses periodically.

1. True
2. False

Q.

The magnetic field strength at a point due to a current carrying circular wire depends on _________.

1. The magnitude of the current flowing through the wire.

2. All the above

3. The distance of the point from the wire.

4. The number of loops the wire has.

Q. ________ states current is induced in a conductor if the magnetic flux linked with the conductor changes.

1. Faraday's law

2. Ampere's law
3. Newton's law
4. Pascal's law

Q. An isolated conducting sphere of radius R maintained at potential Vis being rotated at constant angular velocity omega about one of its diameter.find magnetic dipole momentm(vector)of the sphere and magnetic induction B(vector) at its centre.

Q. The distance between two charge is reduced to 2cm from original distance of 8cm.The force now will increase by which factor?

Q.
When the loop becomes perpendicular to the magnetic field, no current flows through it momentarily as the brush loses contact with the split rings. Then why doesn't the motor stop in this position? IS IT DUE TO THE MOMENTUM PRESENT IN THE LOOP??

Q. 27.A charged particle , having charge q1 accelerated through a potential difference V enters a magnetic field in which it experience a force F and when v is increased to 5V. then find value of Force experienced?

Q. An arc of radius $6\text{m}$ subtends an angle ${120}^{\circ }$ at the centre. If an ant travels on the arc from one end to another end in $4\text{sec}$, what will be the magnitude of average velocity of the ant ?

1. $2\text{m/s}$
2. $\frac{\sqrt{3}}{2}\text{m/s}$
3. $3\text{m/s}$
4. $\frac{3\sqrt{3}}{2}\text{m/s}$

Q.

What is meant by self-induction?

Q.

The variation of potential with distance $R$ from the fixed point is shown in figure.

The electric field at $R=5m$ is

1. $2.5V{m}^{-1}$

2. $-2.5V{m}^{-1}$

3. $0.4V{m}^{-1}$

4. $-0.4V{m}^{-1}$

Q. A conducting circular loop is placed in a uniform magnetic field of $0.04T$ with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at $2mm/s$. The induced emf in the loop when the radius is $2cm$ is

1. $3.2\pi \mu V$
2. $4.8\pi \mu V$
3. $1.6\pi \mu V$
4. $0.8\pi \mu V$

Q. Assertion :An emf $\overrightarrow{E}$ is induced in a closed loop where magnetic flux is varied. The induced $\overrightarrow{E}$ is not a conservative field. Reason: The line integral $\overrightarrow{E}\cdot d\overrightarrow{l}$ around the closed loop is nonzero.

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 conducting circular loop is placed in a uniform magnetic field, $B=0.025T$ with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of $1mm{s}^{-1}$. The induced emf when the radius is $2cm$ is :

1. $2\pi \mu V$
2. $\pi \mu V$
3. $\frac{\pi }{2}\mu V$
4. $2\mu V$

Q.

In Fleming’s right hand rule

1. Thumb - direction of motion

2. All the other options are correct

3. Forefinger - direction of magnetic field

4. Middle finger - direction of induced current

Q. The flux linked with a coil is $0.8Wb$ when a $2A$ current is flowing through it. If this current begins to increase at the rate of $400A/s$, the induced emf in the coil will be

1. $20V$
2. $40V$
3. $80V$
4. $160V$

Q. An aeroplane is flying horizontally with a velocity of $360$ km/h. The distance between the tips of the wings of aeroplane is $25m$. The vertical component of earth's magnetic field is $4\times {10}^{-4}Wb/m^2$. The induced e.m.f. is

1. $1$ V
2. $100$ V
3. $1$ kV
4. Zero

Q. A coil of copper having $1000$ turns is placed in a magnetic field $(B=4\times {10}^{-5})T$ perpendicular to its axis. The cross sectional area of the coil is $0.05m^2$. If it turns through ${180}^o$ in $0.01$ second, then the e.m.f. induced in the coil will be

1. $4V$
2. $0.04V$
3. $0.4V$
4. $0.2V$

Q. Assertion :An electric field $\overrightarrow{E}$ is induced in a closed loop where magnetic flux is varied.The induced $\overrightarrow{E}$ is not a conservative field Reason: The line integral $\overrightarrow{E}.\overrightarrow{dl}$ around the closed loop is nonzero

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. Assertion is incorrect but Reason is correct