JEE Main entrance exam Question Bank Solutions for Physics (JEE Main)

A geyser heats water flowing at a rate of 2.0 kg per minute from 30°C to 70°C. If the geyser operates on a gas burner, the rate of combustion of fuel will be ______ g min^-1.

[Heat of combustion = 8 × 10³ Jg^-1 Specific heat of water = 4.2 Jg^-1°C^-1]

On an X temperature scale, water freezes at -125°X and boils at 375°X. On a Y temperature scale, water freezes at -70°Y and boils at -30°Y. The value of temperature on X scale is ______ on which value of temperature on y Scale becomes 50° Y.

A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500°C and then placed on large ice block. The maximum amount of ice that can melt is ______.

(Specific heat of copper = 0.39 Jg^-1 c^-1, latent heat of 0 fusion of water = 335 Jg^-1)

80 gm of water at 30°C is poured on a large block of ice at 0°C. The mass of ice that melts is ______.

Work done in converting one gram of ice at -10°C into steam at 100°C is ______.

The specific heat of a substance is given by C = a + bT, where a = 1.12 kJ kg^-1K^-1 and b = 0.016 kJ-kg K^-2. The amount of heat required to raise the temperature of 1.2 kg of the material from 280 K to 312 K is ______.

A converging lens of focal length f is placed at a distance 0.3 m from an object to produce an image on a screen 0.9 m from the lens. With the object and the screen in the same positions, an image of the object could also be produced on the screen by placing a converging lens of focal length.

In normal adjustment, for a refracting telescope, the distance between objective and eye piece is 30 cm. The focal length of the objective, when the angular magnification of the telescope is 2, will be ______.

500 g of water and 100 g of ice at 0°C are in a calorimeter whose water equivalent is 40 g. 10 g of steam at 100°C is added to it. Then water in the calorimeter is ______.

(Latent heat of ice = 80 cal/g, Latent heat of steam = 540 cal/g)

A slab consist of two parallel layers of copper and brass of the same thickness and having thermal conductivities in the ratio 1 : 4. If the free face of brass is at 100°C and that of copper at 0°C, the temperature of interface is ______.

A ring consisting of two parts ADB and ACB of same conductivity K carries an amount of heat H. The ADB part is now replaced with another metal keeping the temperatures T₁ and T₂ constant. The heat carried increases to 2H. What should be the conductivity of the new ADB part? (Given `"ACB"/"ADB"` = 3)

Two rectangular blocks A and B of different metals have same length and same area of cross-section. They are kept in such a way that their cross-sectional area touch each other. The temperature at one end of A is 100°C and that of B at the other end is 0°C. If the ratio of their thermal conductivity is 1 : 3, then under steady state, the temperature of the junction in contact will be ______.

A thin square steel plate with each side equal to 10 cm is heated by a blacksmith. The rate of radiated energy by the heated plate is 1134 watts. The temperature of the hot steel plate is ______.

(Stefan's constant σ = 5.67 × 10^-8 watt m^-2K^-4 emissivity of the plate = 1)

An electric heater is used in a room with a total wall area of 137 m² to maintain a temperature of +20°C inside it when the outside temperature is -10°C. The walls have three different layers of materials. The innermost layer is of wood of thickness 2.5 cm, the middle layer is of cement of thickness 1.0 cm and the outermost layer is brick of 25.0 cm. The power of the electric heater will be ______ W. Assume that there is no heat loss through the floor and the ceiling. The thermal conductivities of wood, cement, and brick are 0.125, 1.5, and 1.0 watt/m/°C respectively.

As per the given figure, two plates A and B of thermal conductivity K and 2 K are joined together to form a compound plate. The thickness of plates are 4.0 cm and 2.5 cm respectively and the area of cross-section is 120 cm² for each plate. The equivalent thermal conductivity of the compound plate is `(1+5/alpha)`K, then the value of a will be ______.

A charged particle 'q' is shot towards another charged particle 'Q' which is fixed, with a speed 'v'. It approaches 'Q' upto a closest distance r and then returns. If q were given a speed of '2v' the closest distances of approach would be ______.

The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is ______ cm.

When monochromatic red light is used instead of blue light in a convex lens, its focal length will ______.

A cylinder of radius R made of material of thermal conductivity K₁ is surrounded by a cylindrical shell of inner radius R and outer radius 3R made of a material of thermal conductivity K₂. The two ends of the combined system are maintained at two different temperatures. What is the effective thermal conductivity of the system?

A capacitor is connected to a 20 V battery through a resistance of 10 Ω. It is found that the potential difference across the capacitor rises to 2 V in 1 µs. The capacitance of the capacitor is ______ µF. Given: In `(10/9)` = 0.105