Magnetic Effects Of Current Test

Result

Magnetic Effects Of Current Test - 4

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Question 1
1 / -0

A coil has 2000 turns and area of 70cm².The magnetic field perpendicular to the plane of the coil is 0.3wb /m²and takes 0.1 sec to rotate through 180^o. The value of the induced e.m.f. will be

A
8.4V

B
84V

C
42V

D
4.2V

Solution

⇒ e = 84 V
Question 2
1 / -0

A point source of electromagnetic radiation has an average power output of 800W. The maximum value of electric field at a distance 3.5m from the source will be:

A
56.7 V/m

B
62.6 V/m

C
39.3 V/m

D
47.5 V/m

Solution

Intensity of electromagnetic wave given is by
Question 3
1 / -0

To establish an instantaneous displacement current of 2A in the space between two parallel plates of 1µF capacitor, the potential difference across the capacitor plates will have to be changed at the rate of:

A
4 × 10⁴ V/s

B
4 × 10⁶ V/s

C
2 × 10⁴ V/s

D
2 × 10⁶ V/s

Solution
Question 4
1 / -0

The angle of dip at a place is 60^o . A magnetic needle oscillates in a horizontal plane at this place with period T. The same needle will oscillate in a vertical plane coinciding with the magnetic meridian with a period

A
T

B
2T

C
T/2

D
T/√2

Solution

When needle oscillates in horizontal plane

Then it's time period is

When needle oscillates in vertical plane i.e. It oscillates in total earth's total magnetic field (B)
Question 5
1 / -0

A closely wound coil of 100 turns and area of cross-section 1cm² has a coefficient of self-induction 1 mH. The magnetic induction in the centre of the core of the coil when a current of 2A flows in it, will be

A
0.022 Wbm^-2

B
0.4 Wb m^-2

C
0.8 Wb m^-2

D
1Wb m^-2

Solution
Question 6
1 / -0

A conducting ring of mass m kg and radius r is placed on a smooth horizontal plane. The ring carries a current i. A horizontal magnetic field is switched on at time t = 0 as shown in figure. The initial angular acceleration of the ring will be

A

B

C

D

Solution
Question 7
1 / -0

Two infinite length wires carries currents 8A and 6A respectively and placed along X and Y-axis. Magnetic field at a point P(0,0,d)m will be

A

B

C

D

Solution

Magnetic field at P
Question 8
1 / -0

A proton of mass m and charge +e is moving in a circular orbit of a magnetic field with energy 1MeV. What should be the energy of α-particle (mass = 4 m and charge =+2e), so that it can revolve in the path of same radius

A
1 MeV

B
4 MeV

C
2 MeV

D
0.5 MeV

Solution
Question 9
1 / -0

Earth's magnetic field may be supposed to be due to a small bar magnet located at the centre of the earth. If the magnetic field at a point on the magnetic equator is 0.3×10^–4T. Magnet moment of bar magnet is

A
7.8 10⁸ amp×m²

B
7.8 × 10²² amp × m²

C
6.4 × 10²² amp × m²

D
None of these

Solution

When a magnet is freely suspended in earth’s magnetic field, it's north pole points north, so the magnetic field of the earth may be suppose to be due to a magnetic dipole with it's south pole towards north and as equatorial point is on the broad side on position of the dipole.
Question 10
1 / -0

A square loop of side ‘a’ and resistance R is placed in a transverse uniform magnetic field B. If it suddenly changes into circular form in time t then magnitude of induced charge will be

A

B

C

D

Solution