Magnetism and Matter — Physics STD 12 Science — Question

A radioactive sample has half-life of 5 years. Probability of decay in 10 years will be

(a) 100%

(b) 75%

(c) 50%

(d) 25%

A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is

(a) B

(b) 2 B

(c) 4 B

(d) B/2

An object is placed at a distance u from a simple microscope of focal length f. The angular magnification obtained depends:

1. On f but not on u.
2. On u but not on f.
3. On f as well as u.
4. Neither on f nor on u.

Which of the following pairs of physical quantities may be represented in the same unit?

1. Heat and temperature.
2. Temperature and mole.
3. Heat and work.
4. Specific heat and heat.

Which of the following figures correctly shows the phase relation between the input signal and the output signal of triode amplifier

(a)	(b)
(c)	(d)

A wire of length L and 3 identical cells of negligible internal resistances are connected in series.  Due to current, the temperature of the wire is raised by ∆ T in a time t.  A number N of similar cells is now connected in series with a wire of the same material and cross – section but of length 2 L.  The temperature of the wire is raised by the same amount ∆ T in the same time t.  the value of N is

(a) 4

(b) 6

(c) 8

(d) 9

In the circuit shown below E₁ = 4.0 V, R₁ = 2 W, E₂ =  6.0 V, R₂ = 4 W and R₃ = 2 W.  The current  I₁ is

(a) 1.6 A

(b) 1.8 A

(c) 1.25 A

(d) 1.0 A

The peak voltage in a 220V AC source is:

When the resistance of 9 W is connected at the ends of a battery, its potential difference decreases from 40 volt to 30 volt. The internal resistance of the battery is

(a) 6 W

(b) 3 W

(c) 9 W

(d) 15 W

Refractive index of air is 1.0003. The correct thickness of air column which will have one more wavelength of yellow light (6000 Å) than in the same thickness in vacuum is

(a) 2 mm

(b) 2 cm

(c) 2 m

(d) 2 km