An electric motor of mass 40 kg is mounted on four vertical springs each having a spring constant of 4000 Nm-1. The period with which the motor vibrates vertically is
0.314 s
3.14 s
0.628 s
0.157 s
An observer is approaching a stationary source with a velocity th of the velocity of sound. Then the ratio of the apparent frequency to actual frequency of source is
4 : 5
5 : 4
2 : 3
3 : 2
When a wave travels in a medium, the particle displacement is given by the equation where a, b and c are constants. The maximum particle velocity will be twice the wave velocity, if
b = ac
A progressive wave is reflected by a rigid wall at x = 0. Then the reflected wave can be represented by
y = A sin (kx + ωt)
y = A cos (kx + ωt)
y = − A sin (kx − ωt)
y = − A sin (kx + ωt)
A heater of 220 V heats a volume of water in 5 min. The same heater when connected to 110 V heats the same volume of water in (minute)
5
20
10
2.5
Which one of the following graphs represents the variation of electric field with distance r from the centre of a charged spherical conductor of radius R?
Two conducting spheres A and B of radius a and b respectively are at the same potential. The ratio of the surface charge densities of A and B is
A.
Given electric potential of spheres are same ie,
VA = VB
Surface charge density
Three charges 2q, -q, -q are located at the vertices of an equilateral triangle. At the circumcentre of the triangle
the field is zero but potential is non-zero
potential is zero and the field is infinity
the field is non-zero but potential is zero
both the field and potential are non-zero
C,V,U and Q are capacitance, potential difference, energy stored and charge of a parallel plate capacitor respectively. The quantities that increase when a dielectric slab is introduced between the plates without disconnecting the battery are
V and C
V and U
U and Q
V and Q