# Dependence on Area and Orientation

## Trending Questions

**Q.**A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced emf is

- Twice per revolution
- Once per revolution
- Four times per revolution
- Six times per revolution

**Q.**A circular coil of radius 10 cm is placed in a uniform magnetic field of 3.0×10–5 T with its plane perpendicular to the field initially. It is rotated at constant angular speed about an axis along the diameter of the coil and perpendicular to the magnetic field so that it undergoes half of the rotation in 0.2 s. The maximum value of EMF induced (in μV) in the coil will be close to the integer

**Q.**A rectangular, square, circle and elliptical loop, all in xy− plane, are moving out of a uniform magnetic field with a constant velocity V=v^i. The magnetic field is directed along negative z− axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

- any of the four loops
- the rectangular, circular & elliptical loops.
- the circular and elliptical loops
- only the elliptical loop

**Q.**The figure shows a conducting loop being pulled out of a uniform magnetic field with a constant speed v. Which of the four plots, shown in the figure, may represent the power delivered by the pulling agent as a function of the constant speed v.

- A
- B
- C
- D

**Q.**A current carrying loop of radius R and current I is placed in uniform magnetic field B perpendicular to its plane. What is the tension developed in the wire?

**Q.**The coil of area 0.1 m2 has 500 turns. After placing the coil in a magnetic field of strength 4× 10−4Wb/m2, if rotated through 90∘ in 0.1 s, the average emf induced in the coil is

- 0.2 V
- 0.1 V
- 0.012 V
- 0.05 V

**Q.**

A coil of area 80cm2 and 50 turns is rotating with 2000 revolutions per minute about an axis perpendicular to a magnetic field of 0.05 Tesla. The maximum value of the e.m.f. induced in it is

**Q.**A flat coil of 500 turns, each of area 50 cm2, rotates in a uniform magnetic field of 0.1 Wb/m2 about an axis normal to the field at an angular speed of 150 rad/s. (Initially magnetic field was along the area vector of the field). The coil has a resistance of 15 Ω. Maximum induced current in the coil is

- 1.5 A
- 2.5 A
- 3.5 A
- 4.5 A

**Q.**A coil having 500 turns of square shape each of side 10 cm is placed normal to a magnetic field which is increasing at 1T/s. The induced emf is:

- 0.1V
- 0.5V
- 1V
- 5V

**Q.**A circular conducting loop of radius r0 and having resistance per unit length λ is placed in a magnetic field B which is constant in space and time as shown in the figure. The ends of the loop are crossed and pulled in opposite directions with a velocity v such that the loop always remains circular and the radius of the loop goes on decreasing, then :

- Radius of the loop changes with time t as r=r0−vtπ
- EMF induced in the loop as a function of time is E=2Bv[r0−vtπ]
- Current induced in the loop is I=Bv2πλ
- Current induced in the loop is I=Bvπλ

**Q.**

A long solenoid of radius $R$ carries a time $\left(t\right)$ dependent current $I\left(t\right)={I}_{0}t(1\xe2\u02c6\u2019t)$. A ring of radius $2R$ is placed coaxially near its middle. During the time instant $0\xe2\u2030\xa4t\xe2\u2030\xa41$, the induced current $\left({I}_{R}\right)$ and the induced$EMF\left({V}_{R}\right)$ in the ring changes as:

Direction of $IR$ remains unchanged and ${V}_{R}$ is maximum at$t=0.5$

Direction of$IR$ remains unchanged and ${V}_{R}$ is zero at$t=0.25$

At $t=0.5$ direction of $IR$ reverses and ${V}_{R}$ is zero

At $t=0.25$ direction of $IR$ reverses and ${V}_{R}$ is maximum

**Q.**A long straight rod AB of length 2 m moves in a uniform magnetic field of magnitude B=0.5 T with a velocity of 10 ms−1 as shown in the figure. Find the emf induced in the rod.

- 5 V
- 6 V
- 10 V
- 1.5 V

**Q.**A wire of irregular closed shape is turned into a circular shape as shown in the figure. Determine the direction of flow of induced current in the loop if the magnetic field is constant.

- Clockwise
- Anticlockwise
- First clockwise then anticlockwise
- No current will be induced

**Q.**A square loop of side l enters a region of transverse magnetic field with a constant speed v as shown in the figure. The resistance of the loop is r. Choose the graph that represents the variation of induced current (i) across the loop versus time. [Given, d>2l]

**Q.**A semicircular conducting ring of radius R is placed in the xy plane, as shown in the figure. A uniform magnetic field is set up along the X-axis. No net EMF will be induced in the ring, if

- it moves along the X-axis
- it moves along the Y-axis

- it moves along the Z-axis
- it remains stationary

**Q.**A rectangular, a square, a circular and an elliptical loop, all in the (x−y) plane, are moving out of a region of uniform magnetic field, with a constant velocity, →V=v^i. The magnetic field is directed along the negative z− direction. The induced emf, during the passage of these loops out of the region of magnetic field, will not remain constant for:

- Any of the four loops
- The rectangular, circular and elliptical loops
- The circular and the elliptical loops
- Only the elliptical loop

**Q.**The figure shows a conducting circular loop of radius 20 cm placed in a uniform magnetic field 1.5 T perpendicular to the plane of the loop. A semicircular wire OP is pivoted at the center O and the other end touches the loop at P. The center O and a fixed point Q, on the loop, are connected by a resistor of 10 Ω. Resistance of semicircular wire and the circular loop is negligible. Find the current flowing through the resistor, if the semicircular loop is rotating with a constant angular velocity of 5 rad/s.

- 0.045 A
- 0.035 A
- 0.015 A
- 0.025 A

**Q.**The number of turns in the coil of AC generator is 5000, and the area of the coil is 0.25 m2. The coil is rotated at the rate of 100 ( cycles / sec) in a magnetic field of 0.2 Wb m−2. The peak value of emf generated is nearly

- 766 kV
- 440 kV
- 157 kV
- 210 kV

**Q.**Consider the following statements about the Oersted experiment.

Statement P: The magnetic field due to a straight current carrying conductor is in the form of circular loops around it.

Statement Q:The magnetic field due to a current carrying conductor is strong at far points from the conductor, compared to the near points.

- Both P and Q are true
- P is true but Q is false
- P is false but Q is true
- Both P and Q are false

**Q.**A copper rod ab of length l, pivoted at one end a, rotates at constant angular velocity ω, at right angle to a uniform magnetic field B. c is the midpoint of the rod. What will be the ratio of induced emf across ac to cb?

- 3:2
- 2:3
- 3:1
- 1:3

**Q.**A square loop of edge length a is placed in the same plane as long straight wire carrying current i. The center of the loop is at distance r from wire where r>>a. If loop is moved away from the wire at a constant velocity of v induced emf in the loop is

- Î¼0iv2Ï€
- Î¼0iav2Ï€r
- Î¼0ia2v2Ï€r2
- Î¼0ia3v2Ï€r3

**Q.**

A coil of radius 10 cm and resistance 40Ω has 1000 turns. It is placed with its plane vertical and its axis parallel to the magnetic meridian. The coil is connected to a galvanome ter and is rotated about the vertical diameter through an angle of 180∘. Find the charge which flows through the galvanometer if the horizontal component of the earth's magnetic field is BH=3.0×10−5T.

**Q.**AB is a resistanceless conducting rod which forms a diameter of a conducting ring of radius r rotating in a uniform magnetic field B as shown in the figure. The resistance R1 and R2 do not rotate. Then current through the resistor R1 is -

- Bωr22R1
- Bωr22R2
- Bωr22R1R2(R1+R2)
- Bωr22(R1+R2)

**Q.**A metallic rod of length l is tied to a string of length 2l and made to rotate with angular speed ω on a horizontal table with one end of the string fixed at point O. If there is a vertical magnetic field B in the region, the e.m.f induced across the ends of the rod is:

- 3Bωl22
- 4Bωl22
- 5Bωl22
- 2Bωl22

**Q.**The figure shows a conducting ring of radius R. A uniform steady magnetic field B lies perpendicular to the plane of the ring in a circular region of radius r(<R). If the resistance per unit length of the ring is λ, then the current induced in the ring when its radius gets doubled is

- 2BRλ
- BRλ
- Zero
- Br24Rλ

**Q.**A coil of radius 10cm and resistance 40Ω has 1000 turns. It is placed with its plane vertical and its axis parallel to the magnetic meridian. The coil is connected to a galvanometer and is rotated about the vertical diameter through an angle of 180o. Find the charge which flows through the galvanometer if the horizontal component of the earth's magnetic field is B=3.0×10−5T

**Q.**A metal rod of resistance 20Ω is fixed along a diameter of a conducting ring of radius 0.1 m and 1 on x – y plane. There is an magnetic field →B=50T^k. The ring rotates with an angularvelocity ω=20rads−1 about its axis. An external resistance of 10Ω is connected across the centre of the rod and rim. The current through external resistance is

- Zero
- =14A
- =12A
- =13A

**Q.**nt7. Two identical long conducting wires AOB and COD are placed at right angle to each other, with one above otherntsuch that O is their common point for the two. The wires carry I1and I2 currents, respectively. Point P is lyingntat distance d from O along a direction perpendicular to the plane containing the wires. The magnetic field at thentpoint P will ben

**Q.**A conducting square loop of side l and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A uniform and constant magnitude field B exists along the perpendicular to the plane of the loop as shown in figure. The current induced in the loop is

- zero
- 2BlvR anti-clockwise
- BlvR clockwise
- BlvR anti-clockwise

**Q.**A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced emf is

- Twice per revolution
- Four times per revolution
- Six times per revolution
- Once per revolution