The current sensitivity of a moving coil galvanometer depends on

the number of turns in the coil
moment of inertia of the coil
current sent through galvanometer
eddy current in Al frame

Solution

Current sensitivity = \(\frac{nBA}{k}\)

where K is constant of torsional rigidity.

In cyclotron the gyro radius is

proportional to momentum
proportional to energy
inversely proportional to momentum
inversely proportional to energy

Solution

\(Bqv=\frac{mv^{2}}{r}\Rightarrow r=\frac{mv}{Bq}\)

A circular loop of area 0.02 m² carrying a current of 10A, is held with its plane perpendicular to a magnetic field induction 0.2 T. The torque acting on the loop is

0.01 Nm
0.001 Nm
zero
0.8 Nm

Solution

Torque on loop τ = nIAB cos θ; Here θ= 90º

∴ τ = 0.

A proton, deutron and an -particle enter a magnetic field perpendicular to field with same velocity. What is the ratio of the radii of circular paths?

1: 2: 2
2 :1 : 1
1: 1: 2
1 :2 : 1

Solution

\(r=\frac{mv}{Bq}\, or,r\alpha \frac{m}{q}\) for the same value of v and B.

A cathode ray beam is bent in a circle of radius 2 cm by a magnetic induction 4.5 × 10^–3 weber/m². The velocity of electron is

3.43 × 10⁷m/s
5.37 × 10⁷m/s
1.23 × 10⁷m/s
1.58 × 10⁷m/s

Solution

An electron (mass =9 × 10^–31kg, charge =1.6 × 10^–19C)moving with a velocity of 10⁶m/s enters a magnetic field. If it describes a circle of radius 0.1m, then strength of magnetic field must be

4.5 × 10^–5 T
1.4 × 10^–5 T
5.5 × 10^–5 T
2.6 × 10^–5 T

Solution

A solenoid of length 1.5 m and 4 cm diameter possesses 10 turns per cm. A current of 5A is flowing through it, the magnetic induction at axis inside the solenoid is

(μ₀ = 4π × 10^-7 weber amp^-1 m^-1)

4π × 10^-5 gauss
2π × 10^-5 gauss
4π × 10^-5 tesla
2π × 10^-5 tesla

Solution

B = μ₀nI = 4π × 10^-7 × 10 × 5 = 2π × 10^-5 T

A current carrying conductor placed in a magnetic field experiences maximum force when angle between current and magnetic field is

3 π/4
π/2
π/4
zero

Solution

F= iB l sin θ. This is maximum when sin θ = 1 or θ = π/2.

An electron enters a region where magnetic field (B) and electric field (E) are mutually perpendicular,then

it will always move in the direction of B
it will always move in the direction of E
it always possesses circular motion
it can go undeflected also

A current carrying coil is subjected to a uniform magnetic field. The coil will orient so that its plane becomes

inclined at 45° to the magnetic field
inclined at any arbitrary angle to the magnetic field
parallel to the magnetic field
perpendicular to the magnetic field

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