The phase difference between the instantaneous velocity and acceleration of a particle executing simple harmonic motion is:

• 0.5π

• π

• 0.707 π

• 0.707 π

A vertical spring with force constant k is fixed on a table. A ball of mass m at a height h above the free upper end of the spring falls vertically in the spring. so that the spring is compressed by a distance d. The net work done in the process is:

What is the value of inductance L for which the current is a maximum in a series LCR circuit with C =10μ F and ω = 1000 s^-1

• 100 mH

• 1 mH

• cannot bec calculated unless R is known

• cannot bec calculated unless R is known

Three point charges +q, - 2q and +q are placed at points (x = 0, y = a, z = 0), (x = 0, y = 0, z = 0) and (x = a, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are :

•  along +y direction
•  qa along the line joining points
  
  (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

• qa along the line joining points
  
  (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

• qa along the line joining points
  
  (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

The total power dissipated in watts in the circuit shown here is:

• 16

• 40

• 54

• 54

The resistance of an ammeter is 13 Ω  and its scale is graduated for a current up to 100 A. After an additional shunt has been connected to this ammeter it becomes possible to measure currents up to 750 A by this meter. The value of shunt resistance is.

• 20 Ω

• 2 Ω

• 0.2 Ω

• 0.2 Ω

Under the influence of a uniform magnetic field. a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion.

• depends on v and not on R

• depends on both R and v

• is independent of both R and v

• is independent of both R and v

28.

The primary and secondary coil of a transformer have 50 and 1500 turns respectively. If the magnetic flux Φ linked with the primary coil is given Φ = Φ_o +4t, where Φ is in weber, t is time is second and Φ_o is a constant the output voltage across the secondary coil is:

• 90 V

• 120 V

• 220 V

• 220 V

Two condensers, one of capacity C and the of capacity C/2, are connected to a V volt battery, as shown.



This work done in charging fully both the condensers is:

• 2 CV²

• CV²/4

• 3CV²/4

• 3CV²/4

A transforner is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately:

• 30%

• 50 %

• 90 %

• 90 %