CBSE
Multiple Choice QuestionsAn electric current passes through a long straight copper wire. At a distance 5 cm from the straight wire, the magnetic field is B. The magnetic field at 20 cm from the straight wire would be
A toroid having 200 turns carries a current of 1A. The average radius of the toroid is 10 cm. The magnetic field at any point in the open space inside the toroid is
4 × 10-3 T
0.5 × 10-3 T
0
3 × 10-3 T
A rectangular coil of area A, having number of turns N is rotated at f revolutions per second in a uniform magnetic field B. The maximum emf induced in the coil is
fNB
2fNBA
fBA
fNBA
A cell is connected between the points A and C of a circular conductor ABCD with O as centre and angle AOC = 60°. If B1 and B2 are the magnitudes of the magnetic fields at O due to the currents in ABC and ADC respectively, then ratio is
1
2
5
6
An iron rod of volume 10-4 m3 and relative permeability 1000 is placed inside a long solenoid having 5 turns/cm. If a current of 5.0 A is passed through the solenoid, then magnetic moment of the rod is
20 A-m2
25 A-m2
30 A-m2
35 A-m2
An electron having mass 9.1 x 10-31 kg moves in a circular path of radius 0.4 m with velocity 105 m/s in a magnetic field. The strength of magnetic field is
1.56 × 10-5 T
1.62 × 10-4 T
1.42 x 10-6 T
1.88 × 10-5 T
A current of 0.4 A is passed through the coil of galvanometer having 500 turns and each turn has an average area of 3 x 10-4 m2 . If a torque of 2 Nm is required for this coil carrying some current to set it parallel to a magnetic field then the strength of magnetic field will be
31 T
33.34 T
32 T
40 T
A galvanometer has a resistance of 4 Ω and a full scale deflection is produced by 12 mA current. What resistance must be connected in series with it to enable it to read 1.2 V ?
45 Ω
96 Ω
80 Ω
40 Ω
In a uniform magnetic field, an -shaped metal frame is located perpendicular to the plane of the conductor and varying with time at the rate (dB /dt)=0.20 T/s. A conducting connector starts moving with an acceleration a = 30 cm/s along the parallel bars of the frame. The length, l of the conductor is equal to 44 cm. If at the moment t = 0, the loop area and magnetic induction are equal to zero, then the emf induced in the loop t = 1s after the beginning of motion is
6 × 10-4 V
8 × 10-2 V
6 × 10-2 V
12 × 10-3 V
In a hydrogen atom, the electron is making 6.6 × 1015 rps in a circular path of radius 0.53 . What is the magnetic induction produced at the centre of orbit ?
6.3 T
12.6 T
18.9 T
25.2 T
