Class 12th

A radioactive sample has an average life of 30ms and is decaying. A capacitor of capacitance 200 µF is first charged and later connected with resistor 'R'. If the ratio of charge on capacitor to the activity of radioactive sample is fixed with respect to time then the value of 'R' should be _______ Ω.

In Bohr's atomic model, the electron is assumed to revolve in a circular orbit of radius 0.5 Å. If the speed of electron is 2.2 * 10? m/s, then the current associated with the electron will be _______ * 10?² mA. [Take π as 22/7]

In a uniform magnetic field, the magnetic needle has a magnetic moment 9.85 * 10?² A/m² and moment of inertia 5 * 10? kg m². If it performs 10 complete oscillations in 5 seconds then the magnitude of the magnetic field is _______ mT. [Take π² as 9.85]

The amplitude of upper and lower side bands of A.M. wave where a carrier signal with frequency 11.21 MHz, peak voltage 15 V is amplitude modulate by a 7.7 kHz sine wave of 5 V amplitude are (a/10) V and ( b/10 ) V respectively. Then the value of a/b is _______.

A particle of mass 9.1 * 10?³¹ kg travels in a medium with a speed of 10? m/s and a photon of a radiation of linear momentum 10?²? kg m/s travels in vacuum. The wavelength of photon is _______ times the wavelength of the particle.

Consider an electrical circuit containing a two way switch 'S'. Initially S is open and then T? is connected to T?. As the current in R = 6Ω attains a maximum value of steady state level, T? is disconnected from T? and immediately connected to T?. Potential drop across r = 3Ω resistor immediately after T? is connected to T? is _______ V. (Round off to the Nearest Integer)

A prism of refractive index n? and another prism of refractive index n? are stuck together (as shown in the figure). n? and n? depend on λ, the wavelength of light, according to the relation:
n? = 1.2 + (10.8 * 10?¹?)/λ² and n? = 1.45 + (1.8 * 10?¹?)/λ²
The wavelength for which rays incident at any angle on the interface BC pass through without bending at that interface will be _______ nm.

A circular conducting coil of radius 1 m being heated by the change of magnetic field B passing perpendicular to the plane in which the coil is laid. The resistance of the coil is 2μΩ. The magnetic field is slowly switched off such that its magnitude changes in time as B = (4/π) * 10?³ T [1 - ( t/100 )]. The energy dissipated by the coil before the magnetic field is switched off completely is E = _______ mJ.

A transistor is connected in common emitter circuit configuration, then collector supply voltage is 10 V and the voltage drop across a resistor of 1000Ω in the collector is 0.6 V. If the current gain factor (β) is 24, then the base current is _______ µA. (Round off to the Nearest Integer)

The value of aluminium susceptibility is 2.2 * 10?. The percentage increase in the magnetic field if space within a current carrying toroid is filled with Aluminium is x/10?. Then the value of x is _______.