Question 2 :
Which of the following is the main reason of Opacity of light waves.<br/>
Question 4 : <div>Fill in the blanks:</div>An image formed by _________ mirror is always of the same size as that of object.
Question 7 :
The magnification produced by a mirror is $\displaystyle \frac{1}{3}$ then the type of mirror is ...............................
Question 8 :
A student obtains a blurred image of an object on a screen by using a concave mirror. In order to obtain a sharp image on the screen, he will have to shift the mirror:
Question 9 :
The image of our face in a plane mirror is :
Question 10 :
<span>What happens when you throw a ray of light on the mirror along the normal?</span>
Question 11 :
An object is placed at a distance of 1.5 m from a screen and a convex lens is interposed between them. The magnification produced is 4. The focal length of the lens is then
Question 12 :
A ray of light going towards the centre of curvature of a convex mirror ............
Question 13 :
<span>The plane through the focus perpendicular to the axis of a mirror or lens is</span>
Question 15 :
In a concave mirror, if the position of the object is at the centre of curvature then where will be the image formed?
Question 17 :
<span>The relation between potential difference (V) and current (I) was discovered by : </span>
Question 18 :
A current of 300 mA is made to flow through a 6k$\Omega$ resistor. What is the potential difference across the resistor?<br/>
Question 19 :
If $n$ is the number density of free electrons in a metallic wire, then the resistance is proportional to
Question 21 :
Three heaters each rated $250 \ W$, $100 \ V$ are connected in parallel to a $100 \ V$ supply. The energy supplied in $kWh$ to the three heaters in $5 \ hours$ is :
Question 22 :
How many electrons constitute current of one micro ampere in one second?
Question 23 :
A table lamp of power $60 \ W$ consumed 9 (commerical) units of electricity in the month of April. For how many hours per day, on an average, was the lamp in use?
Question 24 :
The ratio of the concentration of electrons to that of holes in a semiconductor is $\dfrac{7}{4}$, then what is the ratio of their drift velocities:<br/>
Question 25 :
In an electrical circuit three incandescent bulbs A, B and C of rating 40 W, 60 W and 100 W respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?<br><br>
Question 26 :
An electric motor operating on $50 V$ D.C. supply draws a current of $10 A$. If the efficiency of the motor is $40\%$, then the resistance of the winding of the motor is:<br/>
Question 27 :
Four bulbs, each of rating $(100 W, 220 V)$ and connected in parallel across a voltage supply of $220 V,$ are operated for five hours daily. If all the bulbs are replaced by LEDs of rating $(8 W, 220 V)$, how many units of electrical energy will be saved every month ($30$ days)? 
Question 28 :
The length of a given cylindrical wire is increased by $100\%$. Due to the consequent decrease in diameter, the change in the resistance of the wire will be<br>
Question 29 :
When $5V$ potential difference is applied across a wire length $0.1\ m$, the drift speed of electron is 2.5 $\times 10^{-4} ms^{-1}$. If the electron density in the wire is 8 $\times 10^{28} m^{-3}$, the resistivity of the material is close to
Question 30 :
An electric bulb is connected to a $20$ V battery of negligible internal resistance. The resistance offered by the bulb is $5$ $\Omega$. The electrical energy consumed by the bulb in $3$ hours is _____ kWh.
