Four identical electrical lamps are labelled 1.5V, 0.5A which describes the condition necessary for them to operate at normal brightness. A 12V battery of negligible internal resistance is connected to lamps as shown, then
The value of R for normal brightness of each lamp is
The value of R for normal brightness of each lamp is
Total power dissipated in circuit when all lamps are normally bright is 24W
Power dissipated in R is 21W when all lamps are normally bright
When the rms voltages V_{L}, V_{C} and V_{R} are measured respectively across the inductor L, the capacitor C and the resistor R in a series LCR circuit connected to an AC source, it is found that the ratio V_{L} : V_{C} : V_{R }= 1 : 2 : 3. If the rms voltage of the AC source is 100 V, then V_{R} is close to :
50 V
70 V
90 V
100 V
What is the fractional error in g calculated from ? Given the fractional error in T and l are x and y respectively.
x+y
x-y
2x+y
2x-y
Three masses m, 2m and 3m are moving in x-y plane with speed 3u, 2u, and u respectively as shown in figure. The three masses collide at the same point at P and stick together. The velocity of resulting mass will be :
A small ball of mass m starts at a point A . with speed v_{o} and moves along a frictionless track AB as shown. The track BC has coefficient of friction . The ball comes to stop at C after travelling a distance L which is :
Which of the following is not based on the principle of capillarity
Floating of wood on eater surface
Ploughing of soil
Rise of oil in wick of lantern
Soaking of ink by bloating paper
When the angle of contact between a solid and a liquid is 90°, then
Cohesive force > Adhesive force
Cohesive force < Adhesive force
Cohesive force = Adhesive force
Cohesive force >> Adhesive force
When impurities are added to an elastic substance, its elasticity
Increases
Decreases
Becomes zero
May increase or decrease
What is the change in surface energy, when a mercury drop of radius R splits up into 1000 droplets of radius r?
Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by 75 × 10^{-4} N, forces due to the weight of the liquid. If the surface tension of water is 6 × 10^{-2} N/m, the inner-circumference of the capillary must be
There is no change in the volume of a wire due to change in its length on stretching. The poison’s ration of the material of the wire is
+ .50
- 0.50
0.25
- 0.25
There is a hole in the bottom of tank having water. If total pressure at bottom is 3 atm (1 atm = 10^{5}N/m2) then the velocity of water flowing from hole is
10 m/s
30 m/s
20 m/s
none of these
The work done in blowing a soap bubble of radius R is W_{1} and that to a radius 3R is W_{2}. the ratio of work done is
1:3
3:1
1:9
9:1
One end of a uniform wire of length L and of weight W is attached rigidly to a point on the roof and a weight W_{1} is suspended from its lower end. If S is the area of cross-section of the wire, the stress in the wire at a height 3L/4 from its lower end is,
In the following fig. is shown the flow of liquid through a horizontal pipe. Three tubes A, B and C are connected to the pipe. The radii of the tubes A, B and C at the junction are respectively 2 cm, 1 cm and 2 cm. It can be said that the
Height of the liquid in the tube A is maximum
Height of the liquids in tubes A and B are same
Height of the liquids in all three tubes are same
Height of the liquids in tubes A and C are same
An incompressible liquid flows through a horizontal tube as shown in the following fig. Then the velocity v of the fluid is
3.0 m/s
1.5 m/s
1.0 m/s
none of these
A stretched wire has a Young’s modulus and energy density E. The strain in the stretched wire is
A small sphere of mass m is dropped from a great height. After it has fallen 100 m, it has attained its terminal velocity and continues to fall at that speed. The work done by air friction against the sphere during the first 100 m of fall is
Greater than the work done by air friction in the second 100 m
Less than the work done by air friction in the second 100 m
Equal to 100 mg
Greater than 100 mg
A sheet can be made water proof by coating it with a substance that changes the angle of contact
to
to zero
from acute to obtuse
from obtuse to acute