Physics - Online Test
Q1. A particle having charge 100 times that of an electron is revolving in a circular path of radius 0.8 m with one rotation per second. Magnetic field produced at the centre of the circular path is
Answer : Option C
Explaination / Solution:
A charge moving in a circular path is equivalent to a current Since the particle has charge 100 times e and it makes 1 revolution per second,q=100e and T=1s.
The magnetic field at the centre
The magnetic field at the centre
Q2. Three voltmeters, all having different resistances, are joined as shown. When some potential difference is applied across A and B, their readings are V1, V2 , V3 .
Answer : Option D
Explaination / Solution:
V3 and combination of V1 and V2 (V1 + V2) are connected in parallel so potential in V3 must be equal to potential in (V1 + V2)
the potential difference across AB = = +.
Q3. The period of a spring oscillating simple harmonically is
Answer : Option D
Explaination / Solution:
No Explaination.
Q4. If is the intensity after the first Polaroid the intensity emerging from the second Polaroid kept at an angle to the first is given by
Answer : Option A
Explaination / Solution:
As per malus law when a beam of completely plane polarised light i passed through the analyser the intensity of transmitted light varies directly as the square of cosine of angle between the plane of polariser and analyser.
Q5.
A toroid wound with 60.0 turns/m of wire carries a current of 5.00 A. The torus is iron, which has a magnetic permeability of under the given conditions. H and B inside the iron are
Answer : Option B
Explaination / Solution:
No Explaination.
Q6. A p-n junction has a thickness of the order of
Answer : Option B
Explaination / Solution:
The width of depletion layer depends on the nature of semiconductor and doping concentration of the two sides of p-n junction. If the doping concentration is small, the width of p-n junction is large and vice-versa. Thus the width of p-n junction will be of the order of to .
Q7. Name the instrument used to measure instantaneous speed of a vehicle.
Answer : Option D
Explaination / Solution:
A speedometer or a speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the 1900s, and as standard equipment from about 1910 onwards.
Speedometers for other vehicles have specific names and use other means of sensing speed. For a boat, this is a pit log. For an aircraft, this is an airspeed indicator.
Charles Babbage is credited with creating an early type of a speedometer, which were usually fitted to locomotives.
Q8. A sound wave has frequency 500 Hz and velocity 350m/s. What is the distance between the two particles having phase difference of 60
Answer : Option D
Explaination / Solution:
No Explaination.
Q9. A parallel plate capacitor made of circular plates each of radius R = 6.0 cm has a capacitance C = 100 pF. The capacitor is connected to a 230 V ac supply with a (angular) frequency of 300 rad . rms value of the conduction current is
Answer : Option C
Explaination / Solution:
No Explaination.
Q10. Given magnetic field B, area A and length l of a solenoid. The magnetic energy per unit volume is
Answer : Option C
Explaination / Solution:
U=12μ0B2Al
UV=B22μ0
