Magnetism And Matter — Physics STD 12 Science — Question

Consider the following statements:

1. An emf can be induced by moving a conductor in a magnetic field.
2. An emf can be induced by changing the magnetic field.

1. Both A and B are true.
2. A is true but B is false.
3. B is true but A is false.
4. Both A and B are false.

A piece of cloud having area 25   and electric potential of  volts. If the height of cloud is 0.75 km, then energy of electric field between earth and cloud will be

(a) 250 J

(b) 750 J

(c) 1225 J

(d) 1475 J

A charged particle moves along a circle under the action of possible constant electric and magnetic fields. Which of the following are possible?

A listener is at rest with respect to the source of sound. A wind starts blowing along the line joining the source and the observer. Which of the following quantities do not change?

1. Frequency.
2. Velocity of sound.
3. Wavelength.
4. Time period.

A capacitor is charged to 200 volt it has 0.1 coulomb charge. When it is discharged, energy will be

(a) 1 J

(b) 4 J

(c) 10 J

(d) 20 J

A source of sound moves towards an observer.

1. The frequency of the source is increased.
2. The velocity of sound in the medium is increased.
3. The wavelength of sound in the medium towards the observer is decreased.
4. The amplitude of vibration of the particles is increased.

Coherent sources of light produce constructive interference while there is a phase difference between them is :

The quantities that remain conserved in a nuclear reaction :

36 cells, each of emf 4V are connected in series and kept in a box. The combination shows an emf of 88V on the outside. Calculate the number of cells reversed.

In an LCR circuit the potential difference between the terminal of the inductance is 60V, between the terminals of the capacitor is 30V and that between the terminals of the resistance is 40V. The supply voltage will be equal to: