Physics - Online Test
Q1. Predict the polarity of the capacitor in the situation described by fig.
Answer : Option B
Explaination / Solution:
A will become positive with respect to B because current indused is in clockwise direction
Q2. Planck’s constant has the dimensions of
Answer : Option B
Explaination / Solution:
Plank Constant and Angular momentum both have same dimension
Q3. If the radius of earth reduces by 4% and density remains same then escape velocity will
Answer : Option C
Explaination / Solution:
Escape velocity ve α Rρ−−√and if density remains constant⇒ve α RSo if the radius reduces by 4% then escape velocity also reduces by 4%
Q4. Repeaters used in electronic communication generally
Answer : Option A
Explaination / Solution:
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it.Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction.A repeater is a combinatin of a transmitter,an amplifier and retransmits it to the receiver somtimes witha a change of carrier frequency.
Q5. A passenger arriving in a new town wishes to go from the station to a hotel located 10 km away on a straight road from the station. A dishonest cabman takes him along a circuitous path 23 km long and reaches the hotel in 28 min. What is (a) the average speed of the taxi, (b) the magnitude of average velocity?
Answer : Option D
Explaination / Solution:
(a) Total distance travelled = 23 km
Total time taken = 28 min = h
∴ Average speed of the taxi =
(b) Distance between the hotel and the station = 10 km = Displacement of the car
∴ Average velocity =
Q6. A Gaussian sphere encloses an electric dipole within it. Total flux across the sphere is
Answer : Option D
Explaination / Solution:
Q7.
A steel wire of length 4.7 m and cross-sectional area 3.0 stretches by the same amount as a copper wire of length 3.5 m and cross-sectional area of 4.0 under a given load. What is the ratio of the Young’s modulus of steel to that of copper?
Answer : Option D
Explaination / Solution:
No Explaination.
Q8.
A geyser heats water flowing at the rate of 3.0 liters per minute from 27 C to 77 C. If the geyser operates on a gas burner, what is the rate of consumption of the fuel if its heat of combustion is 4.0 J/g?
Answer : Option B
Explaination / Solution:
m = mass of water
s = specific heat of water
heat of combustion is 4.0 J/g
rate of consumption of the fuel = Q / Heat of combustion
Q9. The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained?
Answer : Option A
Explaination / Solution:
Heat energy required for burning of casing of rocket comes from the rocket itself. As a result of work done against friction the kinetic energy of rocket continuously deceases and this work against friction reappears as heat energy. This results in reduction of the mass of the rocket.
Q10. What is the shortest wavelength present in the Paschen series of spectral lines?
Answer : Option C
Explaination / Solution:
No Explaination.
