When a biro pen rubbed on a dry silk cloth is moved very close to a piece of paper on a dry table, the pen is found to pick up the paper. This is because

• A. both the pen and the cloth are magnetized
• B. the pen is magnetized but the cloth is not
• C. the pen is charged while the cloth is magnetized
• D. both the pen and the cloth are charged

A stone, Q is thrown with velocity U at an angle of 75^o to the horizontal. Another stone R is thrown with the same velocity U but with an angle of 15^o to the horizontal. The ranges covered by the stones will be

• A. greater for Q
• B. greater for R
• C. the same for Q and R
• D. greater for the heavier of the two stones

A body on the ground is acted on by a force of 10N at a point P as shown in the fig below. What force is needed to stop the body from moving eastwards?

• A. 5N in the direction of east
• B. 5N in the diretion of west
• C. 5V3N in the direction of west
• D. 10N in the southwest direction

(a) Explain briefly dielectric strength.

(b) An electromagnetic wave has its wavelength shorter than those of radiowave and microwave but longer than that of visible light.

(i) Identify the wave.

(ii) Name one suitable detector for the wave.

(iii) Name one source of the wave.

(c) An oil drop carrying a charge of 1.0 x 10\(^{-19 }\)C is found to remain at rest in a uniform electric field of intensity 1200 NC\(^{-1}\). Calculate the weight of the oil drop.

(d) An RLC series circuit consists of a 100\(\Omega\) resistor, 0.05 H inductor and a 25 \(\mu\) capacitor. A 220 V, 50 Hz mains voltage is applied across the circuit. Calculate the:

(i) impedance;

(ii) current. (\(\pi\) = 3.14)

A sound of frequency 512 Hz reaches a listener 100 m away. If the sound travels in air at s.t.p., what is its wavelength?

[speed of sound in air = 331 m/s]

• A. 1.550m
• B. 0,646m
• C. 5.120m
• D. 0.195m

The terrestrial telescope has one extra lens more than the astronomical telescope. The extra lens is for

• A. improving the sharpness
• B. creating an inverted image
• C. magnification of the image
• D. erection of the image

Two bar magnets are placed near each other. Which of the following diagrams correctly illustrates the magnetic field pattern formed by the pair?

• A. I
• B. II
• C. III
• D. IV

In which of the following device is the expansion of solid not required?

I. Simple pendulum II. Fire alarms III. Thermostat IV. Bimetallic thermometer

• A. III only
• B. II & III only
• C. I only
• D. II, III & IV only

The inside of a vacuum flak is usually coated with silver to reduce heat loss by

• A. evaporation
• B. radiation
• C. conduction
• D. convention

(a) Explain diffusion.

(b) Give one reason why the rate of diffusion is higher in gases than in liquids at the same temperature.