Unit III: Magnetism and magnetic effects of electric current - Online Test
Q1. 
The BH curve for a ferromagnetic material
is shown in the figure. The material is placed inside a long solenoid which
contains 1000 turns/ cm. The current that should be passed in the solenonid to
demagnetize the ferromagnet completely is
Answer : Option B
Explaination / Solution:
Q2. Two short bar magnets have
magnetic moments 1.20 Am2
and 1.00 Am2
respectively. They are kept on a horizontal table parallel to each other with
their north poles pointing towards the south. They have a common magnetic
equator and are separated by a distance of 20.0 cm. The value of the resultant
horizontal magnetic induction at the mid-point O of the line joining their
centers is (Horizontal components of Earth’s magnetic induction is 3.6 × 10-5 Wb m-2 )
Answer : Option C
Explaination / Solution:
Q3. The vertical component of Earth’s magnetic field at a place is
equal to the horizontal component. What is the value of angle of dip at this
place?
Answer : Option B
Explaination / Solution:
Q4. A flat dielectric disc of radius R carries an excess charge on its surface. The surface charge density is σ. The disc rotates about an axis perpendicular toits plane passing through the center with angular velocity ω. Find the magnitude of the torque on the disc if it is placed in a uniform magnetic field whose strength is B which is directed perpendicular to the axis of rotation
Answer : Option D
Explaination / Solution:
Q5. A simple pendulum with charged bob is oscillating with time period T and let θ be the angular displacement. If the uniform magnetic field is switched ON in a direction perpendicular to the plane of oscillation then
Answer : Option C
Explaination / Solution:
Hint: Both T θ and decreases as B increases.
