Dakshana Mock Test Season XII Solutions

1] A metallic conductor carries 800mA current from left to right. It means that

Answer: 5*10¹⁸ electrons are flowing per second from right to left

2] Ohm's law (I = V/R) is applicable for

Answer: Only metallic conductors of electricity

3] A copper wire has a resistance of 8 ohm. The wire is stretched to double of its original length. Its new resistance will be

Answer: 32 ohm

4] A beam of light traveling in air enters into a liquid. Its speed reduces by 30%. The refractive index of liquid with respect to air is

Answer: 10/7

5] The refractive index of a liquid is 5/3. A ray of light traveling in this liquid falls at interface of liquid and air. At what angle of incidence should it fall on liquid air interface so that, it suffers total internal reflection?

Answer: 53°

6] A beam of light in air is incident upon the smooth plane surface of a piece of flint glass making an angle of 30° with its plane. If the reflected beam and refracted beam are perpendicular to each other, what is the index of refraction of flint glass with respect to air?

Answer: √3

7] The image created by a converging lens is projected on a screen that is 60 cm away from the lens. If the height of the image is one fourth the height of the object, what is focal length of the lens?

Answer: 48cm

8] An electric bulb is marked (60 W, 120 V). What is the resistance of filament of bulb?

Answer: 240Ω

9] A battery whose emf is 40 V has an internal resistance 5Ω. If, this battery is connected across a 15Ω resistor (R), what will be voltage drop across resistor (R) ?

Answer: 30 V

10] Three identical bulbs B₁, B₂ and B₃ are connected in parallel across terminals of an ideal source of emf. What will happen if bulb B₂ burns out?

Answer: Bulb B₁ and B₃ will give same light

11] A bar magnet is cut into two equal parts by cutting it very slowly perpendicular to its length. Which of the following is true?

Answer: Each part will be a bar magnet having two equal and opposite poles same as original magnet

12] Which of the following cannot form a real image for a divergent beam of light?

Answer: All of the above

13] Three resistors of resistance Ω/60, Ω/30 and Ω/20 are joined in parallel. The equivalent resistance of combination will be

Answer: Ω/110

14] A rod of length 5cm lies along the principal axis of the concave mirror of focal length 15cm in such a way that the end of the closer to the pole is 30cm away from it. Then, the length of the image is

Answer: 3.75cm

15] If an object moves towards or away a plane mirror with a velocity 'v' then the image will approach or recede with velocity

Answer: 2v

16] The focal length of a concave mirror depends upon the

Answer: Radius of curvature of the mirror

17] The rainbow is formed due to ___.

Answer: All of the above

18] A person cannot see distinctly any object placed beyond 40cm from his eye. What is the power of the lens which will enable him to see distant stars clearly?

Answer: -2.5D

19] An electrical power station has the power 200 Megawatt (MW), then the electrical energy produced per day will be

Answer: 4800 MWh

20] How many electrons flow per second through the filament of 220V and 110W electric bulb?

Answer: 3.125 * 10¹⁸

21] The S.I. unit of electrical resistivity is

Answer: ohm * m

22] A bulb of 100 Watt, 250 Volt has the resistance of

Answer: 625 ohm

23] A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R₁, then the ratio R / R₁ is

Answer: 25

24] Magnetic effect of current were discovered by

Answer: Oersted

25] An electron enters a magnetic field at right angles to it as shown in figure. The direction of force acting on electron will be