21.

Two sound waves with wavelengths 5.0 m and 5.5 m respectively, each propagate in a gas with velocity 330 m/s. We expect the following number of beats per second

• 12

• 0

• 1

• 1

A transverse wave propagating along x-axis is represented by:


where x is in metres and t is in seconds. The speed of the wave is

•  m/s
• 
• 
• 

The time of reverberation of a room A is one second. What will be the time (in seconds) of reverberation of a room, having all the dimensions double of those of room A?

• 2

• 4

• 
• 

Which one of the following statements is true?

• Both light and sound waves in air are transverse

• The sound waves in air are longitudinal while the light waves are transverse

• Both light and sound waves in air are longitudinal

• Both light and sound waves in air are longitudinal

In the circuit shown, if a conducting wire is connected between points A and B, the current in this wire will

• flow from A to B

• flow in the direction which will be decided by the value of V

• be zero

• be zero

When a charged particle moving with velocity  is subjected to a magnetic field of induction , the force on it is non-zero. This implies that

• angle between  is necessarily 

• angle between  can have any value other than 

• angle between  can have any value othe than zero and 

• angle between  can have any value othe than zero and 

Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances r₁ and r₂ (r₁ > r₂) respectively. When the circuit is closed, the potential difference across the first cell is zero, The value of R is

Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potential difference applied across them so that the magnetic field at their centres is the same?

• 3

• 4

• 6

• 6

The core of a transformer is laminated because

• energy losses due to eddy currents may be minimised

• the weight of the transformer may be reduced

• rusting of the core may be prevented

• rusting of the core may be prevented

Two coils of self-inductances 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is

• 10 mH

• 6 mH

• 4 mH

• 4 mH