List of practice Questions

Which of the statement is true for p-type semiconductors.

In an n-type silicon, which of the following statement is true:

If the current in an electric bulb decreases by 0.5% then power in the bulb changes by
Henry’s law constant for the molality of methane in benzene at 298 K is \(4.27 \times 105\, mm\, Hg\). Calculate the solubility of methane in benzene at 298 K under 760 mm Hg.
19.5 g of \(CH_2 FCOOH\) is dissolved in 500 g of water. The depression in the freezing point of water observed is \(1.00\degree C\). Calculate the van’t Hoff factor and dissociation constant of fluoroacetic acid.
Calculate the depression in the freezing point of water when 10 g of \(CH_3CH_2CHClCOOH\) is added to 250 g of water. \(K_a = 1.4 × 10^{–3} , K_f = 1.86 K kg mol^{–1} .\)
A charged 30 μF capacitor is connected to a 27 mH inductor. What is the angular frequency of free oscillations of the circuit?
A 44 mH inductor is connected to 220 V, 50 Hz ac supply. Determine the rms value of the current in the circuit.
The peak voltage of an ac supply is 300 V. What is the rms voltage? (b) The rms value of current in an ac circuit is 10 A. What is the peak current?
An infinite line charge produces a field of \( 9 × 10^4 NC^{-1} \)at a distance of 2 cm. Calculate the linear charge density.

A 100 W resistor is connected to a 220 V, 50 Hz ac supply. 

(a) What is the rms value of current in the circuit? 

(b) What is the net power consumed over a full cycle?

A point charge of \(2.0\,µC\) is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?
A uniformly charged conducting sphere of \( 2.4\,m\) diameter has a surface charge density of \(80.0\,µCm^{-2}\) . 
(a) Find the charge on the sphere. 
(b) What is the total electric flux leaving the surface of the sphere?
A point charge causes an electric flux of \(−1.0 × 10^3 Nm^2 C^{-1}\) to pass through a spherical Gaussian surface of 10.0 cm radius centered on the charge. 
(a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface? 
(b) What is the value of the point charge?
A 12pF capacitor is connected to a 50V battery. How much electrostatic energy is stored in the capacitor?

Explain what would happen if in the capacitor given in Exercise 2.8, a 3 mm thick mica sheet (of dielectric constant = 6) were inserted between the plates,

(a) while the voltage supply remained connected.

(b) after the supply was disconnected.

(a)and(b)show the refraction of a ray in air incident at 60° with the normal to a glass-air and water-air interface, respectively. Predict the angle of refraction in glass when the angle of incidence in water is 45° with the normal to a water-glass interface
 

Three capacitors of capacitances 2 pF, 3 pF and 4 pF are connected in parallel. 

(a) What is the total capacitance of the combination? 

(b) Determine the charge on each capacitor if the combination is connected to a 100 V supply.

A point charge \(+10 µC\) is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)
 
Although phenoxide ion has more number of resonating structures than carboxylate ion,carboxylic acid is a stronger acid than phenol.Why?

Two charges 2 μC and –2 μC are placed at points A and B 6 cm apart.

(a) Identify an equipotential surface of the system.

(b) What is the direction of the electric field at every point on this surface?

A 4.5cm needle is placed 12cm away from a convex mirror of focal length 15cm. Give the location of the image and the magnification.Describe what happens as the needle is moved farther from the mirror.

Calculate the half-life of a first order reaction from their rate constants given below:

  1.  \(200\  s^{-1 }\)
  2. \(2 \ min^{-1 }\)
  3. \(4\  years^{-1}\)
A regular hexagon of side 10 cm has a charge 5 μC at each of its vertices. Calculate the potential at the centre of the hexagon.
The depression in freezing point of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order given above. Explain briefly.