Download App

Alternating Current — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsAlternating Current4 Marks
Question
A transformer is essentially an a.c. device. It cannot work on d.c. It changes altemating voltages or currents. It does not affect the frequency of a.c. It is based on the phenomenon of mutual induction. A transformer essentially consists of two coils of insulated copper wire having different number of tums and wound on the same soft iron core.
The number of turns in the primary and secondary coils of an ideal transfonner are 2000 and 50 respectively. The primary coil is connected to a main supply of 120V and secondary coil is connected to a bulb of resistance $0.6\Omega.$
  1. The value of voltage across the secondary coil is:
  1. 5V
  2. 2V
  3. 3V
  4. 10V
  1. The value of current in the bulb is:
  1. 7A
  2. 15A
  3. 3A
  4. 5A
  1. The value of current in primary coil is:
  1. 0.125A
  2. 2.52A
  3. 1.51A
  4. 3.52A
  1. Power in primary coil is:
  1. 20W
  2. 5W
  3. 10W
  4. 15W
  1. Power in secondary coil is:
  1. 15W
  2. 20W
  3. 7W
  4. 8W
✓

Answer

  1. (c) 3V

Explanation:

As, $\frac{\text{E}_\text{s}}{\text{E}_\text{p}}=\frac{\text{n}_\text{s}}{\text{n}_\text{p}}$

$\Rightarrow\text{E}_\text{s}=\text{E}_\text{p}\times\frac{\text{n}_\text{p}}{\text{n}_\text{p}}$

$=\frac{120\times50}{2000}=3\text{V}$

  1. (d) 5A

Explanation:

$\text{I}_0=\frac{\text{E}_\text{S}}{\text{R}}\Rightarrow\text{I}_0=\frac{3}{0.6}=5\text{A}$

  1. (a) 0.125A

Explanation:

As, $\frac{\text{I}_\text{P}}{\text{I}_\text{S}}=\frac{\text{E}_\text{S}}{\text{E}_\text{P}}$

$\Rightarrow\text{I}_\text{p}=\frac{\text{E}_\text{S}}{\text{E}_\text{P}}\times\text{I}_\text{S}=\frac{3}{120}\times5=0.125\text{A}$

  1. (d) 15W

Explanation:

Power in primary, PP = EP × IP = 120 × 0.125

= 15W

  1. (a) 15W

Explanation:

Power in secondary coil, PS = ES × IS = 3 × 5

= 15W

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "4 Marks Questions" from Alternating Current→Alternating Current — all question types→Physics STD 12 Science question papers→Bihar Board STD 12 Science question papers→Bihar Board question paper generator→

Similar questions

The electron beam in a colour TV is accelerated through 32kV and then strikes the screen. What is the wavelength of the most energetic X-ray photon?
→
A fat person is standing on a light plank floating on a calm lake. The person walks from one end to the other on the plank. His friend sitting on the shore watches him and finds that the person hardly moves any distance because the plank moves backward about the same distance as the person moves on the plank. Explain.
→
When a fat person tries to touch his toes, keeping the legs straight, he generally falls. Explain with reference to figure.

→
 For the past some time, Aarti had been observing some erratic body movement, unsteadiness and lack of coordination in the activities of her sister Radha, who also used to complain of severe headache occasionally. Aarti suggested to her parents to get a medical check-up of Radha. The doctor thoroughly examined Radha and diagnosed that she has a brain tumour.
  1. What, according to you, are the values displayed by Aarti?
  2. How can radioisotopes help a doctor to diagnose brain tumour? 
→

Solar cell is a p-n junction diode which converts solar energy into electric energy. It is basically a solar energy converter. The upperlayer of solar cell is of p-type semiconductor and very thin so that the incident light photons may easily reach the p-n junction. On the top face of p-layer, the metal finger electrodes are prepared in order to have enough spacing between the fingers for the lights to reach the p-n junction through p-layer.

  1. The schematic symbol of solar cell is:

  1. The p-n junction which generates an emf when solar radiations fall an it, with no external bias applied, is a:
  1. Light emitting diode.
  2. Photodiode.
  3. Solar cell.
  4. None of these.
  1. For satellites the source of energy is:
  1. Solar cell.
  2. Fuel cell.
  3. Edison cell.
  4. None of these.
  1. Which of the following material is used in solar cell?
  1. Barium.
  2. Silicon.
  3. Silver.
  4. Selenium.
  1. The efficiency of a solar cell may be in the range:
  1. 2 to 5%
  2. 10 to 15%
  3. 30 to 40%
  4. 70 to 80%
→
Distance between two successive bright or dark fringes is called fringe width.
$\beta=\text{Y}_\text{n+1}-\text{Y}_\text{n}=\frac{(\text{n}+1)\lambda\text{D}}{\text{d}}-\frac{\text{n}\lambda\text{D}}{\text{d}}=\frac{\lambda\text{D}}{\text{d}}$
Fringe width is independent of the order of the maxima. If whole apparatus is immersed in liquid of refractive index $\mu$ then $\beta=\frac{\lambda\text{D}}{\mu\text{d}}$ (fringe width decreases). Angular fringe width $(\theta)$ is the angular separation between two consecutive maxima or minima
$\theta=\frac{\beta}{\text{D}}=\frac{\lambda}{\text{d}}$
ln the arrangement shown in figure, slit S3 and S4 are having a variable separation Z. Point O on the screen is at the common perpendicular bisector of S1S2 and S3S4.

  1. The maximum number of possible interference maxima for slit separation equal to twice the wavelength in Young's double-slit experiment, is:
  1. Infinite
  2. Five
  3. Three
  4. Zero
  1. ln Young's double - slit experiment if yellow light is replaced by blue light, the interference fringes become.
  1. Wider
  2. Brighter
  3. Narrower
  4. Darker
  1. ln Young's double slit experiment, if the separation between the slits is halved and the distance between the slits and the screen is doubled, then the fringe width compared to the unchanged one will be.
  1. Unchanged
  2. Halved
  3. Doubled
  4. Quadrupled
  1. When the complete Young's double slit experiment is immersed in water, the fringes.
  1. Remain unaltered.
  2. Become wider.
  3. Become narrower.
  4. Disappear.
  1. ln a two slit experiment with white light, a white fringe is observed on a screen kept behind the slits. When the screen is moved away by 0.05m, this white fringe.
  1. Does not move at all.
  2. Gets displaced from its earlier position.
  3. Becomes coloured.
  4. Disappears.
→
A player hits a baseball at some angle. The ball goes high up in space. The player runs and catches the ball before it hits the ground. Which of the two (the player or the ball) has greater displacement?
→
If you are walking on the moon, can you hear the sound of stones cracking behind you? Can you hear the sound of your own footsteps?
→
In how many bands the full range of radiowaves can be divided ? Describe about all the bands in brief.
→
In a children-park an inclined plane is constructed with an angle of incline 45° in the middle part. Find the acceleration of a boy sliding on it if the friction coefficient between the cloth of the boy and the incline is 0.6 and g = 10m/s2.

→