21.

In a coil of resistance 100 Ω, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is

• 250 Wb

• 275 Wb

• 200 Wb

• 200 Wb

In the above circuit the current in each resistance is

• 0.5 A

• 0 A

• 0.25

• 0.25

In the given circuit diagram when the current reaches steady state in the circuit, the charge on the capacitor of capacitance C will be :

• 
• 

• CE

• CE

A capacitance of 2 μF is required in an electrical circuit across a potential difference of 1.0 kV. A large number of 1 μF capacitors are available which can withstand a potential difference of not more than 300 V. The minimum number of capacitors required to achieve this is :

• 24

• 32

• 2

• 2

A diverging lens with the magnitude of focal length 25 cm is placed at a distance of 15 cm from a converging lens of the magnitude of focal length 20 cm. A beam of parallel light falls on the diverging lens. The final image formed is

• real and at a distance of 40 cm from the divergent lens

• real and at a distance of 6 cm from the convergent lens

• real and at a distance of 40 cm from the convergent lens

• real and at a distance of 40 cm from the convergent lens

In a common emitter amplifier circuit using an n-p-n transistor, the phase difference between the input and the output voltages will be

• 135°

• 180°

• 45°

• 45°

An electron beam is accelerated by a potential difference V to hit a metallic target to produce X-rays. It produces continuous as well as characteristic X-rays.If λmin is the smallest possible wavelength of X-ray in the spectrum, the variation of log λ min with log V is correctly represented in

A radioactive nucleus A with a half-life T, decays into a nucleus B. At t = 0, there is no nucleus B. At some time t, the ratio of the number of B to that of A is 0.3. Then, t is given by

• t = T log (1.3)

• 
• 
• 

Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths r = λ₁/λ₂, is given by

• r = 3/4

• r = 1/3

• r = 4/3

• r = 4/3

In a Young's double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is

• 9.75 mm

• 15.6 mm

• 1.56 mm

• 1.56 mm