(c) Let the final temperature be T °C. (d) (i) Mass
(ii) Work function/Threshold energy

### Physics 2011 Solved Question Paper ICSE Previous Year

SECTION-II (40 Marks)

Attempt any four questions from this Section.

Question 5:

(a) (i) What is meant by an ideal machine ?
(ii) Write a relationship between the mechanical advantage (M.A.) and velocity ratio (V.R.) of an ideal machine.
(iii) A coolie carrying a load on his head and moving on a frictionless horizontal platform does no work. Explain the reason why. 

(b) Draw a diagram to show the energy changes in an oscillating simple pendulum.
Indicate in your diagram how the total mechanical energy in it remains constant during the oscillation.     

(c) A uniform metre scale can be balanced at the 70.0 cm mark when a mass of 0.05 kg is hung from the 94.0 cm mark.
(i) Draw a diagram of the arrangement.
(ii) Find the mass of the metre scale. 

(a) (i) A machine with 100% efficiency is called an ideal machine.
(ii) For an ideal machine, M.A. = V.R.
(iii) Because the angle between the force applied (vertically upwards) and displacement of load (along the horizontal) is 90°.
∵      W = Fd cos θ
∴      W = Fd cos 90° = 0

(b) (c) (i) See below diagram. (ii) Question 6:

(a) (i) State the laws of refraction of light.
(ii) Write a relation between the angle of incidence (i), angle of emergence (e), angle of prism (A) and angle of deviation (d) for a ray of light passing through an equilateral prism.  

(b) (i) Suggest one way, in each case, by which we can detect the presence of:
(ii) Give one use of Infrared radiations.  

(c) An object is placed in front of a lens between its optical centre and the focus and forms a virtual, erect and diminished image.
(i) Name the lens which formed this image.
(ii) Draw a ray diagram to show the formation of the image with the above stated characteristics.  

(a) (i) The laws of refraction of light are :
1. The incident ray, the normal and the refracted ray lie in the same plane.
2. The sine of angle of incidence (i) bears a constant ratio with the sine of angle of refraction (r) for a given pair of medium i.e., $\frac { sin\quad i }{ sin\quad r } =\quad constant$
(ii) i + e = A + d.

(b) (i) 1. Mercury rises rapidly if a blackened bulb thermometer is kept in these radiations.
2. By the action of silver chloride solution.
(ii) Use of Infrared radiations : Used for therapeutic purposes by doctors.

(c) (i) Concave lens,
(ii) Question 7:

(a) (i) Name the type of waves which are used for sound ranging.
(ii) Why are these waves mentioned in (i) above, not audible to us ?
(iii) Give one use of sound ranging.  

(b) A man standing 25 m away from a wall produces a sound and receives the reflected sound.
(i) Calculate the time after which he receives the reflected sound if the speed of sound in air is 350 ms-1.
(ii) Will the man be able to hear a distinct echo ? Give a reason for your answer. 

(c) (i) Name two safety devices which are connected to the live wire of a household electrical circuit.
(ii) Give one important function of each of these two devices. 

(a) (i) Ultrasonic waves.
(ii) Ultrasonic waves frequency is above 20,000 Hz whereas human audibility range is only till 20,000 Hz.
(iii) Use of sound ranging: Can be used in Radar.

(b) (i) (ii) Yes, because the least time for distinct echo to be heard is 0.1 second.

(c) (1) Fuse and (2) Switch.
(ii) Fuse is used to limit the flow of current. Switch is used to start or stop the flow of current.

Question 8:

(a) (i) Draw a graph of Potential difference (V) versus Current (I) for an ohmic resistor.
(ii) How can you find the resistance of the resistor from this graph ?
(iii) What is a non-ohmic resistor ? 

(b) (i) An electric bulb is marked 100 W, 250 V. What information does this convey ?
(ii) How much current will the bulb draw if connected to a 250 V supply ? 

(c) Three resistors are connected to a 12 V battery as shown in the figure given below: (i) What is the current through the 8 ohm resistor ?
(ii) What is the potential difference across the parallel combination of 6 ohm and 12 ohm resistor ?
(iii) What is the current through the 6 ohm resistor ?

(a) (i) (ii) Resistance = Slope of the graph
(iii) A non-ohmic resistor is that for which ratio of potential difference to the current in resistor is not same for all values of potential difference or current. A non-ohmic resistor does not follow Ohm’s Law.

(b) (i) It means that if a bulb is given a 250 V supply, it will consume 100 J of energy per second.
(ii) Let P = VI
⇒ $I=\frac { 100 }{ 250 }$
∴ I = 0.4 A

(c) Question 9:

(a) (i) Explain why the weather becomes very cold after a hail storm.
(ii) What happens to the heat supplied to a substance when the heat supplied causes no change in the temperature of the substance ?  

(b) (i) When 1 g of ice at 0 °C melts to form lg of water at 0 °C then, is the latent heat absorbed by the ice or given out by it ?
(ii) Give one example where high specific heat capacity of water is used as a heat reservoir.
(iii) Give one example where high specific heat capacity of water is used for cooling purposes. 

(c) 250 g of water at 30 °C is present in a copper vessel of mass 50 g. Calculate the mass of ice required to bring down the temperature of the vessel and its contents to 5 °C.
Specific latent heat of fusion of ice = 336 x 103 J kg-1.
Specific heat capacity of copper vessel = 400 J kg-1 °C-1.
Specific heat capacity of water = 4200 J kg-1 °C-1.