Bulb A rated 160 W, 40 V and Bulb B rated 40 W, 40 V are connected as shown in the diagram. (a) Calculate the ratio V1 : V2. (b) If bulb A fuses, the current in the circuit remains the same. State True or False.

(a) (i) Which element is used in the lining of the special aprons worn by workers in nuclear power plants? (ii) Why is this element preferred? (b) 2411Na emits a nuclear radiation which does not alter the mass number but is deflected by a magnetic field. Name the type of nuclear radiation emitted by 2411Na. Write the equation for this radioactive decay.

Two persons A and B are standing in front of a cliff in the same line, 170 m apart, as shown in the diagram. Person B fires a gun and hears the echo in 3 s. Then person A, standing in front of B, fires the gun. (Speed of sound in air = 340 m s−1) (a) Calculate: (1) the distance of B from the cliff; (2) the minimum time in which B hears the gunshot fired by A. (b) Fill in the blank: The echo is softer than the original sound due to the decrease in ............... [amplitude / frequency] of the wave.

The diagram shows a wheel with a handle. Two forces, F1 and F2 of equal magnitudes are acting on the handle as shown in the diagram. (a) Which force produces negative moment? (b) Is the wheel in equilibrium? (Yes or No) (c) Justify your answer stated in (b).

The given graph represents the cooling curve of a liquid. (a) State the freezing temperature of the liquid. (b) Name the phase change happening at the region QR. (c) In which state (solid / liquid) does the above substance liberate heat at a faster rate? Justify.

(a) Atmospheric temperature after a hailstorm is greater than the temperature during the hailstorm. State True or False. (b) Which thermal physical quantity of a frying pan changes by making its base heavier? (c) State the principle of Calorimetry.

A type of glass block has a refractive index of 1.8. (a) Calculate the speed of light in this glass. (Given speed of light in air = 3 × 108 m s−1) (b) If the width of this block is doubled, then what will be the speed of light in the block?

A ray of light enters a glass block from air and comes out from the opposite surface. If the angle of refraction at the first surface is not the same as the angle of incidence at the second surface, then: (a) What is the product of the ratio sin i / sin r at the first surface and at the second surface? (b) State whether the opposite surfaces are parallel or not parallel. (c) How did you reach the conclusion in (b) above?

Equal masses of substances A, B and C, each at its melting point, take 5 minutes, 7 minutes and 3 minutes respectively to melt when heated at the same rate. Which has the highest specific latent heat of fusion? (a) A (b) B (c) C (d) All are equal

The equivalent resistance of two resistors R1 and R2 connected in parallel is: (a) (b) (c) (d)

Three cylindrical jars A, B and C contain equal volumes of water up to different heights. Their radii satisfy rB < rA < rC. Which jar produces the shrillest sound when air is blown across its mouth? (a) A (b) B (c) C (d) All produce the same sound

Study the circuit diagram containing lamps L1, L2, L3 and L4. Which lamp can fail without interrupting the glow of the other lamps? (a) L1 (b) L2 (c) L3 (d) L4