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

A leaky parallel plate capacitor is filled completely with a material having dielectric constant K = 5 and electric conductivity σ = 7.4 × 10^-12 Ω^-1 m^-1. If the charge on the plate at the instant t = 0 is q = 8.85 µC, then the leakage current at the instant t = 12 s is ______ × 10^-1 µA.

A capacitor of capacity 2 µF is charged to a potential difference of 12 V. It is then connected across an inductor of inductance 0.6 mH. The current in the circuit at a time when the potential difference across the capacitor is 6.0 V is ______ × 10^-1A.

A capacitor has charge 50 µC. When the gap between the plate is filled with glass wool, then 120 µC charge flows through the battery to capacitor. The dielectric constant of glass wool is ______.

Current versus time and voltage versus time graphs of a circuit element are shown in figure.

The type of the circuit element is ______.

Two identical capacitors are connected as shown and have an initial charge of Q₀. The separation between the plates of each capacitor is d₀. Suddenly the left plate of the upper capacitor and right plate of the lower capacitor start moving with speed v towards the left while the other plate of each capacitor remains fixed. `("given" (Q_0V)/(2d_0) = 10 A)`. The value of current in the circuit is ______ A.

A capacitor with capacitance 5µF is charged to 5 µC. If the plates are pulled apart to reduce the capacitance to 2 µF, how much work is done?

At what temperature a gold ring of diameter 6.230 cm be heated so that it can be fitted on a wooden bangle of diameter 6.241 cm? Both diameters have been measured at room temperature (27°C). (Given: coefficient of linear thermal expansion of gold α_L = 1.4 × 10^-5 K^-1).

Each side of a box made of metal sheet in cubic shape is 'a' at room temperature 'T', the coefficient of linear expansion of the metal sheet is 'α'. The metal sheet is heated uniformly, by a small temperature ΔT, so that its new temeprature is T + ΔT. Calculate the increase in the volume of the metal box.

If the length of a cylinder on heating increases by 2%, the area of its base will increase by ______.

The height of mercury column measured with brass scale at temperature T₀ is H₀. What height H' will the mercury column have at T = 0°C. Coefficient of volume expansion of mercury is γ. Coefficient of linear expansion of brass is α ______.

An anisotropic material has coefficient of linear thermal expansion α₁, α₂ and α₃ along x, y and z-axis respectively. Coefficient of cubical expansion of its material will be equal to ______.

A parallel plate capacitor filled with a medium of dielectric constant 10, is connected across a battery and is charged. The dielectric slab is replaced by another slab of dielectric constant 15. Then the energy of capacitor will  ______.

Length of steel rod so that it is 5 cm longer than the copper rod at all temperatures should be ______ cm.

(α for copper = 1.7 × 10^-5/°C and α for steel = 1.1 × 10^-5/°C)

A metal ball immersed in water weighs w₁ at 0°C and w₂ at 50°C. The coefficient of cubical expansion of metal is less than that of water. Then ______.

A disc is rotating freely about its axis. The percentage change in angular velocity of a disc if temperature decreases by 20°C is ______.

(coefficient of linear expansion of material of disc is 5 × 10^-4/°C)

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

• Assertion A: When a rod lying freely is heated, no thermal stress is developed in it.
• Reason R: On heating, the length of the rod increases. In light of the above statements.

choose the correct answer from the options given below:

If the temperature of the sun were to increase from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on earth to what it was previously will be ______.

A plane mirror is moving with velocity `4hati + 5hatj + 8hatk`. A point object in front of the mirror moves with a velocity of `3hati + 4hatj + 5hatk`. Here `hatk` is along the normal to the plane mirror and facing toward the object. The velocity of the image is ______.

If two plane mirrors are kept at 60° to each other, then the number of images formed by them is ______.

A block of ice of mass 120 g at temperature 0°C is put in 300 gm of water at 25°C. The xg of ice melts as the temperature of the water reaches 0°C. The value of x is ______.

[Use: Specific heat capacity of water = 4200 Jkg^-1K^-1, Latent heat of ice = 3.5 × 10⁵ Jkg^-1]